UNIVERSITY  OF  CALIFORNIA 
LOS  ANGELES 


"pi-    U1e 

GIFT  OF 

55160—21- 


Ordnance  Department  Document  No.  2033 


HANDBOOK  OF  ARTILLERY 

INCLUDING 

MOBILE,    ANTIAIRCRAFT, 

MOTOR    CARRIAGE,    AND 

TRENCH  MATERIEL 


PREPARED  IN  THE  OFFICE  OF 
THE    CHIEF    OF    ORDNANCE 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1921 


OKDNAXCE  DEPARTMENT 

Document  No.  2033 
Office  of  the  Chief  of  Ordnance 


Library 

ar 


WAR  DEPARTMENT, 

WASHINGTON,  July,  1921. 

The  following  publication,  entitled  "  Handbook  of  Artillery,  In- 
cluding Mobile,  Antiaircraft,  Motor  Carriage,  and  Trench  Ma- 
teriel," is  published  for  the  information  and  guidance  of  all  students 
of  the  Ordnance  training  schools,  and  other  similar  educational 
organizations.  The  contents  should  not  be  republished  without 
authority  of  the  Chief  of  Ordnance,  War  Department,  Wash- 
ington, D.  C. 

BY  ORDER  OF  THE   SECRETARY  OF  WAR. 

JOHN  J.  PERSHING. 

General,  Chief  of  /Staff. 
OFFICIAL  : 

P.  C.  HARRIS, 

The  Adjutant  General. 


PREFACE. 


The  data  in  this  book  are  compiled  for  use  in  the  Ordnance  training 
schools  and  other  educational  organizations  where  a  short,  yet  com- 
prehensive, survey  of  the  existing  calibers  and  types  of  guns  and  car- 
riages now  in  use  by  the  United  States  Army  is  desired.  With  this  in 
view,  the  descriptions  and  illustrations  have  been  made  as  simple  as 
possible,  and  technicalities  have  been  reduced  to  a  minimum  so  that 
the  distinctive  features  of  the  various  types  of  artillery  materiel  may 
be  readily  understood. 

This  publication  has  been  prepared  in  the  mobile  gun  carriage  sec- 
tion of  the  Artillery  Division  by  Mr.  Murray  H.  Resni  Coff.  The 
general  discussion  on  the  design  and  characteristics  of  mobile  ar- 
tillery is  intended  for  the  instruction  of  student  officers  and  enlisted 
specialists  schools. 

The  second  edition  of  this  book  is  to  be  distributed  to  various  edu- 
cational institutions  for  a  trial  use  in  their  classes,  and  the  results  of 
this  trial  should  be  productive  of  many  constructive  criticisms  so  that 
the  next  edition  will  more  fully  meet  the  varied  needs  of  the  schools 
and  training  units.  The  intention  is  to  revise  this  book  periodically, 
therefore  suggestions  and  criticisms  are  cordially  invited.  Com- 
munications should  be  addressed  to  the  Chief  of  Artillery  Division, 
Office  of  the  Chief  of  Ordnance,  Washington,  D.  C. 

(4) 


LIST  OF  CONTENTS. 


Page. 

List  of  illustrations 7 

Table  of  equivalents 14 

History  and  development  of  artillery  materiel 15 

Artillery,  classes  of 26 

Mobile  artillery,  types  of 26 

Cannons,  their  functions  and  construction,  including  breech  mechanisms-  29 

Mounts  for  mobile  artillery 35 

Recoil  brakes  and  methods  of  counterrecoil 38 

Aiming  devices  and  sighting  methods 40 

Accompanying  vehicles 53 

37-millimeter  gun  materiel,  model  of  1916 57 

2.95-inch  Vickers-Maxim  mountain  gun  materiel  (with  pack  outfit) 63 

75-millimeter  gun  materiel : 

Model  of  1916  materiel 69 

Model  of  1916  MI  materiel 83 

Model  of  1897  MI  (French)  materiel 87 

Model  of  1917   (British)   materiel 103 

Gun  carriage  limber,  model  of  1917  (British) 115 

Gun  carriage  limber,  model  of  1918 119 

Gun  caisson,  model  of  1918 123 

Gun  caisson  limber,  model  of  1918 125 

3-inch  gun  materiel 127 

Guns,  models  of  1902,  1904,  and  1905,  and  carriage,  model  1902 130 

Gun  limber,  model  of  1902 139 

Gun  caisson,  model  of  1902 ___  141 

Gun  caisson,  model  of  1916 143 

Gun  limber,  model  of  1916 145 

Battery  wagon,  model  of  1902 147 

Battery  wagon,  model  of  1902  MI 148 

Store  wagon,  model  of  1902 149 

Store  wagon,  model  of  1902  MI 150 

Forge  limber,  model  of  1902 152 

Store  limber,  model  of  1902 155 

Forge  limber,  model  of  1902  MI 154 

Store  limber,  model  of  1902  MI 155 

Battery  and  store  wagon,  model  of  1917 156 

Battery  reel,  model  of  1917 159 

Reel,  model  of  1909  MI__  161 

Cart,  model  of  1918 164 

Wheels : 

56-inch    (steel   tired) 167 

57-inch  by  3.5  inch  (rubber  tired) 167 

Reel,  model  of  1917,  for  caissons 168 

Automatic  pole  support 169 

(5) 


523505 


Page. 

105-millimeter  howitzer  materiel  (German) 171 

105-millimeter  howitzer  and  carriage,  model  of  1898-1909  (German)-  173 

105-millimeter  howitzer  caisson  model  1898  (German) 178 

105-millimeter  howitzer  carriage  and  caisson  limber,  model  1893 178 

4.7-inch   gun   materiel 181 

Gun  and  carriage,  model  of  1906 186 

Gun  carriage  limber,  model  of  1905 195 

Gun  caisson,  model  of  1908 198 

Gun  limber,  model  of  1908 200 

Gun  caisson,  model  of  1916 202 

Gun  caisson,  model  of  1917 206 

5-inch,  60-pounder  gun  materiel   (British) 209 

Gun,  Mark  I,  and  carriage,  Mark  II 213 

Gun  carriage  limber,  Mark  II 216 

Ammunition   wagon,   Mark   II 219 

Ammunition  wagon  limber,  Mark  II 223 

155  howitzer  materiel,  model  of  1917   (Schneider) 227 

155  howitzer  materiel,  model  of  1918  (Schneider) 231 

Howitzer  and  carriage,  model  of  1918 236 

Howitzer  carr.'age  limber,  model  of  1918 243 

Howitzer  caisson,  model  of  1918 245 

155  gun  materiel  (Filloux) ,, 249 

Gun  and  carriage,  model  of  1918 254 

Gun  carriage  limber,  model  of  1918 263 

6-inch  gun  materiel,  model  of  1917  (British) . .__  265 

7-inch  naval  tractor  mount,  Mark  V 269 

8-inch  howitzer  materiel   (Vickers) 279 

Howitzers,  Marks  VI  and  Vllli,  and  carriages,  Marks  VI  and  VII__ _  288 

Howitzer  carriage  limber,  model  of  1917  (Vickers) 299 

Firing  platform  and  wagon,  model  of  1917  (Vickers) 301 

9.2-inch   howitzer  materiel    (Vickers) 305 

Howitzer  and  carriages,  Marks  I  and  II 310 

Howitzer   transport   wagon 318 

Howitzer  carriage  transport  wagon 319 

Howitzer  platform  transport  wagon 321 

240-millimeter  howitzer  materiel    (Schneider) 323 

Howitzer  and  carriage,  model  of  1918 329 

Accessories 334 

Transport  wagons  and  limbers 339 

Antiaircraft    artillery 344 

3-inch  antiaircraft  gun  materiel,  model  of  1918 348 

3-inch  antiaircraft  gun  mount,  model  of  1917 363 

75-millimeter  antiaircraft  truck  mount,  model  of  1917 377 

Gun  and  howitzer  motor  carriages 387 

Self-propelled   wheeled   mount   for  3-inch   antiaircraft   gun,   model 

of   1917 390 

Self-propelled  caterpillar,  Mark  II,  for  155  millimeter  gun  (Filloux), 

model  of  1918 392 

155  millimeter  motor  gun  carriage  (Christie),  model  of  1920 397 

Trench  warfare  materiel 

3-inch  Stokes'  trench  mortar,  Mark  I 405 

6-inch  Stokes'  trench  mortar,  Mark  I 409 

Prospectus 414 


LIST  OF  ILLUSTRATIONS. 


Frontispiece. 

English  archer  using  a  long  bow 

Balista  and  catapulta  of  the  Greeks 

Sixteenth-century    artillery 17 

Italian  Cerebotian  of  the  fourteenth  century 18 

The  "  Mons  Meg  "  of  Edinburgh  Castle 19 

German  breech-loading  cannon  of  the  sixteenth  century 19 

French  artillery,  1800-1850 20 

Soldier  firing  a  mortar  and  bombshell  requiring  double  ignition 21 

German  artillery,  1842-1874 22 

Besieging  a  fortified  castle,  sixteenth  century 23 

Recoil  brakes  and  methods  of  counterrecoil : 

Hydraulic  brake  (throttling  bar) 39 

Hydraulic  brake   (valve) 39 

Hydraulic  brake    (central  throttling) 40 

Counterrecoil  mechanism  (spring,  concentric  columns) 41 

Counterrecoil  mechanism   (spring,  telescopic) 41 

Hydro-spring  recoil  system 41 

Hydro-pneumatic  recoil  system  with  floating  piston 42 

Hydro-pneumatic  recoil  system  with  fluid  indirect  compact  with  the 

air 42 

Counterrecoil  mechanism  (hydro-pneumatic,  central  buffing) 43 

Aiming  devices : 

Elevating  systems 47 

Panoramic   sight '. 48 

Gunner's  quadrant 49 

Accompanying  vehicles : 

Tractors  hauling  artillery 52 

75  mm.  gun  carriage,  mounted  on  trailer 54 

37-millimeter  gun  materiel,  model  of  1916: 

Rear  view  of  carriage  in  battery  position 56 

Carriage  and  ammunition  cart,  limbered 57 

Left  side  view  of  tripod  mount  in  battery  position 59 

Tripod  mount  in  firing  position 60 

Gun  disassembled  on  the  march  (wheels  and  axles  left  in  the  rear) 61 

Gun  and  personnel  on  the  march  (ammunition  cart  left  in  the  rear) 62 

2.95-inch  Vickers-Maxim  mountain-gun  materiel  (with  pack  outfit)  : 

Carriage  in  firing  position : 64 

Pack  outfit  on  mule  back 65 

Rear  view  of  carriage  in  battery 66 

Detailed  view  of  gun 67 

Side  view  of  carriage  in  battery 67 

75-millimeter  gun  materiel,  model  of  1916 : 

Front  view  of  carriage 

Right  side  elevation  of  carriage 70 

(7) 


8 

T5-millimeter  gun  materiel,  model  of  1916 — Continued.  Page. 

Rear  view  of  carriage . 71 

Plan  view  of  carriage 72 

Left  side  view  of  carriage 7.; 

Breech    mechanism 76 

Gun  at  maximum  elevation 77 

Longitudinal  section  of  recoil  and  counterrecoil  mechanism 78 

Elevating  mechanism T'.i 

Traversing  mechanism 80 

Carriage  and  limber  in  traveling  position .__  81 

75-millimeter  gun  materiel,  model  of  1916  MI : 

Left  and  right  elevations ___  82 

Cradle  assembly  and  longitudinal  section 83 

Left  side  view  in  firing  position 84 

Right  side  view  in  firing  position 85 

Arrangement  of  elevating  mechanisms 86 

75-millimeter  materiel,  model  of  1897  MI  (French)  : 

Left  rear  view  of  carriage 

Front  view  of  carriage 90 

Longitudinal  section  of  gun  and  carriage 92 

Breech   mechanism 93 

Left  side  view  of  carriage 94 

Right  side  elevation  of  carriage 95 

Traversing  and  brake  operating  mechan  sm 96 

Abatage  positions  of  carriage 98 

Plan  view  of  carriage 99 

Sight,  model  of  1901 100 

75-millimeter  gun  materiel,  model  of  1917  (British)  : 

Left  side  elevation  of  carriage 102 

Front  view  of  carriage 103 

Rear  and  front  elevations  of  carriage 104 

Rear  view  of  carriage Hi." 

Breech   mechanism 107 

Recoil-controlling  system 108 

Elevating  and  range  gear 111 

Traversing  gear 112 

75-millimeter  gun  carriage  limber,  model  of  1917  (British)  : 

Front  view  of  limber 115 

Right  side  elevation  of  limber 116 

Rear  and  front  elevations 117 

Rear  view  of  limber 118 

75-millimeter  gun  carriage  limber,  model  of  1918 : 

Rear  view  of  limber 120 

Front  view  of  limber 120 

Assembled  views  of  limber 121 

75-millimeter  gun  caisson,  model  of  1918 : 

Assembled  views  of  gun  caisson 122 

Front  view  of  caisson 123 

Gun  caisson  and  gun  caisson  limber,  limbered 124 

75-millimeter  gun  caisson  limber,  model  of  1918 : 

Front  view  of  caisson  limber 125 

Assembled  views  of  gun  caisson  limber 126 


9 

3-inch  gun  materiel,  model  of  1902 :  Page. 

Front  view  of  carriage 128 

Rear  view  of  carriage 128 

Left  side  elevation  of  carriage 129 

Gun,  models  of  1902,  1904,  and  1905 131 

Breech   mechanism ; 132 

Recoil-controlling   mechanism 134 

Carriage  and  limber,  hauled  by  tractor 135 

Carriage  and  limber  in  traveling  position 135 

Range  quadrant 136 

Rear  sight 137 

3-inch  gun  limber,  model  of  1902 : 

Rear  view  of  limber 139 

3-inch  gun  caisson,  model  of  1902 : 

Front  view  of  caisson 141 

3-inch  gun  caisson,  model  of  1916 : 

Front  view,  showing  door  swung  upward  exposing  ammunition 143 

Front  and  side  elevations  of  caisson 144 

3-inch  gun  caisson  limber,  model  of  1916 : 

Side  and  rear  elevations  of  caisson  limber 146 

Battery  wagon,  model  of  1902  MI : 

Rear  view  of  battery  wagon 147 

Store  wagon,  model  of  1902 : 

Side  view  of  store  wagon 149 

Side  view  showing  store  wagon  and  limber,  limbered 151 

Forge  limber,  model  of  1902  MI : 

Top  view  showing  interior  of  forge  limber 152 

Assembled  views  of  forge  limber 153 

Store  limber,  model  of  1902  MI : 

Top  view  showing  interior  of  store  limber 155 

Battery  and  store  wagon,  model  of  1917 : 

Rear  right  side  view  of  battery  and  store  wagon 156 

Assembled  views  of  battery  and  store  wagon 157 

Battery  reel,  model  of  1917 : 

Left  side  view  of  battery  reel 159 

Reel,  model  of  1909  MI : 

Rear  view  of  reel 161 

Assembled  views  of  reel 162 

Front  view  of  reel 163 

Cart,  model  of  1918 : 

View  showing  reel  and  cart,  1'uibered 164 

Rear  view  of  cart 164 

Assembled  views  of  cart 165 

56-inch  wheel : 

Side  view  of  wheel 167 

Reel,  model  of  1917,  for  caissons : 

View  showing  reel  mounted  on  caisson 168 

Front  and  side  elevations  of  reel 169 

Automatic  pole  support : 

Sectional  diagram  of  pole  support 169 

105-millimeter  howitzer  materiel,  model  of  1898-09  (German)  : 

Left  side  view  of  carriage  in  battery  position 170 

View  showing  carriage  limber  and  caisson  coupled 172 

Front  view  showing  brakes  and  traveling  lock 173 


10 

105-millimeter  howitzer  materiel,  model  of  1898-09  (German)— Contd.  Page. 

Longitudinal  section  of  recoil  mechanism 174 

Equilibrator  mechanism 176 

Rear  view  of  carriage 177 

Front  and  rear  view  of  carriage  limber iT'.i 

Front  and  rear  view  of  caisson 180 

4.7-inch  gun  materiel,  model  of  1916 : 

View  showing  carriage  and  limber  in  traveling  position 181 

Left  side  view  of  carriage  in  battery 182 

Assembled  views  of  carriage  equipped  with  tire  brakes 183 

Left  front  view  of  carriage  equipped  with  band  brakes 184 

Assembled  views  of  carriage  equipped  with  band  brakes 185 

Front  view  of  carriage  equipped  with  tire  brakes 186 

Breech  mechanism 186 

Firing    mechanism 187 

Longitudinal  section  of  gun  and  carriage 188 

Front  view  of  carriage  equipped  with  band  brakes 189 

Rear  right  view  of  carriage 190 

Elevating  and  traversing  mechanisms 190 

Range  quadrant 191 

Rear  view  of  carriage  equipped  with  tire  brakes 192 

Rear  sight 193 

Front  view  of  carriage  equipped  with  tire  brakes 194 

4.7-inch  gun  carriage  limber,  model  of  1905  : 

Front  view  of  limber l«,- 

Assembled  views  of  limber 196 

4.7-inch  gun  caisson,  model  of  1908 : 

Right  side  view  of  caisson 198 

4.7-inch  gun  limber,  model  of  1908: 

View  showing  gun  caisson  and  limber,  limbered 200 

4.7-inch  gun  caisson,  model  of  1916 : 

Right  front  view  showing  chest  doors  open  exposing  diaphragms 202 

Assembled  views  of  gun  caisson 203 

Front  view  of  gun  caisson 204 

4.7-inch  gun  caisson,  model  of  1917: 

Assembled  views  of  gun  caisson 207 

5-inch    (60-pounder)    gun   materiel    (British)  : 

Rear  left  view  of  carriage  in  battery 209 

Carriage  and  limber  in  traveling  position 210 

View  showing  trail  connected  to  limber 211 

Rear  right  view  of  carriage 214 

5-inch   (60-pounder)   gun  carriage  limber,  Mark  II   (British)  : 

Front  view  of  carriage  limber 216 

Rear  view  of  carriage  limber 217 

5-inch  (60-pounder)  ammunition  wagon,  Mark  II  (British)  : 

Front  view  of  ammunition  wagon ' 219 

Rear  view  of  ammunition  wagon 

Ammunition  wagon  and  ammunition  wagon  limber,  limbered 222 

5-inch  (60-pounder)  ammunition  wagon  limber,  Mark  II  (British)  : 

Front  view  of  ammunition  wagon  limber 

Rear  view  of  ammunition  wagon  limber 

155-millimeter  howitzer  materiel,  model  of  1917  (Schneider)  : 

Right  side  view  of  carriage  in  traveling  position 

Carriage  in  battery  position  (rear  view) 228 


11 

155-millimeter  howitzer  materiel,  model  of  1917  (Schneider)— Continued,  .rage. 

Front  view  of  carriage  in  battery  position 

Side  view  of  carriage  en  route 229 

155-millimeter  howitzer  materiel,  model  of  1918  (Schneider)  : 

Traveling  position  of  carriage  and  limber 230 

Assembled  views  of  traveling  position 

Detail  view   of  howitzer 234 

Breech   mechanism 235 

Firing  mechanism 237 

Recoil  and  counterrecoil  mechanism 238 

Longitudinal  section  of  howitzer  and  carriage '    240 

Quadrant    sight 241 

155-millimeter  howitzer  carriage  limber,  model  of  1918  (Schneider)  : 

Plan  and  right  side  elevations 244 

155-millimeter  caisson,  model  of  1918   (Schneider)  : 

Rear  view  of  caisson 245 

General  assembled  views 246 

Front  view  of  caisson 248 

155-millimeter  gun  materiel,  model  of  1918   (Filloux)  : 

Traveling  position  (right  side) 249 

Left-side  view  of  carriage  and  limber  in  traveling  position 250 

Preparing  carriage  for  battery  position 251 

Carriage  in  traveling  position   (rear  view) 251 

Longitudinal  section  of  gun  and  carriage 252 

Maximum  elevation  of  gun 254 

Breech  mechanism 255 

Breech  mechanism  and  counterbalance  cylinder 256 

Carriage  in  firing  position 257 

Rear  view  of  carriage  in  traveling  position 258 

Accessories  and  caterpillar  wheel  shoes 259 

Elevating  and  traversing  mechanism 260 

Caterpillar   adapters 261 

155-millimeter  gun  carriage  limber,  model  of  1918  (Filloux)  : 

Front  view  of  limber,  showing  caterpillar  wheel  shoes,  mounted  on 

wheels , 7 262 

Front  view  of  limber 263 

Detailed   view   of  limber 264 

6-inch  gun  materiel,  model  of  1917  (British)  : 

Plan  view  of  carriage 266 

Left-side  elevation  of  carriage 267 

7-inch  naval  tractor  mount,  Mark  V : 

Carriage  and  limber  in  traveling  position  (front  view) 269 

Rear  view  of  carriage 270 

Left-side  view  of  carriage  in  battery 271 

Carriage  and  limber  in  traveling  position  (rear  view) 273 

Top  carriage  and  axle  details 274 

Assembled  view  of  hydraulic  brake 275 

View  of  axle  mounted  in  track  layer 276 

Side  elevation  of  track  layer 277 

Carriage  in  battery  position,  showing  maximum  elevation  of  gvm 278 

8-inch  howitzer  materiel  (Vickers)  : 

Carriage  in  battery  position  (Mark  VI) 279 

Carriage  and  limber  in  traveling  position  (rear  view) 280 

Carriage  in  battery  position  (Mark  VII) 282 

Rear  view  of  carriage,  showing  maximum  elevation  of  howitzer 284 


12 

8-inch  howitzer  materiel  (Vickers) — Continued.  Page. 

Right-side  view  of  carriage  in  battery 285 

Left-side  elevation  of  Mark  VI  carriage 287 

Rear  right-side  of  carriage  in  firing  position 288 

Detailed  view  of  howitzer  (Mark  VI) 289 

Breech  mechanism  of  Mark  VI  howitzer 290 

Breech  block 291 

Firing    mechanism 292 

Front  view  of  howitzer  carriage 293 

Elevating  and  traversing  mechanism 294 

Howitzer  carriage  mounted  on  firing  platform 295 

Sight  assembled 296 

Caterpillar   adapters 298 

8-inch  howitzer  carriage  limber,  firing  platform  and.  wagon,  model  of  1917 
(Vickers)  : 

Limber  in  traveling  position  (front  view) 300 

Materiel  6n  train  and  in  battery 302 

9.2-inch  howitzer  materiel  (Vickers)  : 

Carriage  in  battery  position 304 

Left  side  elevation  of  carriages  assembled 306 

Front  view,  showing  maximum  elevation  of  howitzer 307 

Loading  position,  showing  shell  on  tray 308 

Longitudinal  section  of  carriage 309 

Rear  view  of  carriage,  showing  howitzer  at  miximum  elevation 310 

Breech  mechanism   (Mark  I) 311 

Breech  mechanism   (Mark  II) 312 

Gear  regulating  recoil 313 

Method  of  loading,  showing  loading  gear  mechanism  in  action 314 

Right-side  view  of  carriage  in  battery 314 

Traversing  gear 315 

Sight  assembled 316 

9.2-inch  howitzer  transport  wagon  (Vickers)  : 

Method  of  mounting  howitzer 318 

Materiel  6n  train 320 

240-millimeter  materiel,  model  of  1918  (Schneider)  : 

Materiel  £n  train __.  322 

Front  view  of  carriage,  showing  maximum  elevation  of  howitzer 323 

Carriage  in  loading  position 324 

Method  of  loading  the  howitzer  with  rammer  car 326 

Left  elevation  of  carriage  with  howitzer  at  maximum  elevation 327 

Breech   mechanism 328 

Mounting  the  cradle 330 

Recoil  and  recuperator  mechanism 331 

Elevating  and  quick-loading  gear  mechanism 332 

Mouting  the  top  carriage 333 

Method  of  lowering  platform . 334 

Sight  assembled ^ 335 

Erecting  frame  in  position 330 

Left  side  view  of  carriage 338 

240-millimeter  howitzer  transport  limbers  and  wagons : 

Howitzer  transport  wagon 339 

Cradle  transport  wagon 339 

Mounting  the  howitzer 340 

Top  carriage  transport  wagon ; 341 

Platform  transport  wagon 341 


13 

Antiaircraft  artillery :  Page. 

Antiaircraft  artillery  in  action 345 

3-inch  antiaircraft  gun  materiel,  model  of  1918 : 

Carriage  in  traveling  position 347 

Carriage  in  battery  position  (front  view) 349 

View  showing  outriggers  folded 350 

Longitudinal  section  of  carriage 351 

Breech   mechanism 352 

View  showing  right  rear  outrigger  with  jack  spade  and  float  removed-  354 

Side  view  of  carriage  in  battery  position 355 

Assembled  view  showing  carriage  in  firing  position 357 

Front  view  of  trailer 358 

Sight  on  left  side  of  carriage 359 

Sight  on  right  side  of  carriage 360 

3-inch  antiaircraft  gun  mount,  model  of  1917 : 

Longitudinal  section  of  gun  mount 362 

View  showing  mount  in  action 363 

Right  side  elevation  of  gun  mount 364 

View  showing  right  side  of  mount 365 

Breech   mechanism 367 

Vertical  section  showing  breech  open 368 

Elevating  and  traversing  mechanisms 371 

Left  side  elevation  of  gun  mount 372 

75-millimeter  antiaircraft  truck  mount,  model  of  1917 : 

Plan  view  of  truck  mount 376 

Truck  in  traveling  position  (right  side  view) 377 

Sectional  elevation  of  gun  mount 378 

View  showing  truck  mount  in  action 379 

Gun  mount  showing  gun  at  maximum  elevation •_ 382 

Truck  in  traveling  position  (left  side  view) 383 

Firing  and  stability  jacks 385 

Truck  mount  in  battery  position. 386 

Gun  and  howitzer  motor  carriages : 

105-millimeter  howitzer  motor  carriage,  model  of  1920 387 

3-inch  antiaircraft  wheeled  mount  showing  gun  at  maximum  eleva- 
tion  ' ; 388 

Self-propelled  wheeled  mount  for  3-inch  antiaircraft  gun,  model  of  1917 : 

Left  side  view  of  mount  in  traveling  position 390 

Self-propelled   caterpillar   Mark    II,    for   155-millimeter   gun    (Filloux), 
model  of  1918 : 

Plan  view 392 

Traveling  position,  front  view 394 

Traveling  position,  rear  view 395 

155-millimeter  motor  gun  carriage  (Christie),  model  of  1920: 

Side  elevation  of  mount  in  traveling  position 397 

Rear  view  of  mount  in  battery  position 399 

Trench  warfare  materiel : 

Trench  warfare 402 

Arrangement  of  trenches 403 

3-inch  Stokes's  trench  mortar,  Mark  I : 

Mortar  in  action 405 

Front  view  of  trench  mortar 406 

Rear  view  of  trench  mortar__ 407 

6-inch  trench  mortar,  Mark  I : 

Methods  of  installation  of  trench  mortar 410 

Left  side  view  of  mortar 411 

Method  of  loading  trench  mortar 412 

Rear  view  of  mortar__  413 


TABLE  OF  EQUIVALENTS. 


1  mil 3.37  minutes. 

1  degree 17.  777  mils. 

1  meter  (m) 39.37  inches. 

1  centimeter  (cm) 0.3937  inch. 

1  millimeter  (mm) 0.03937  inch. 

1  kilogram  (kg) 2.2046  pounds. 

1  dekagram  (dk) 0.3527  ounce. 

1  gram 15.432  grains. 

1  liter 1.05671  quarts  (U.  S.). 

1  quart  (U.  S.) 0.9463  liter. 

1  inch 2.54  centimeters. 

1  foot 0.3048  meter. 

1  yard 0.9144  meter. 

1  square  inch 6.452  square  centimeters. 

1  kilogram  (kg)  per  square  centimeter 14.223  pounds  per  square  inch. 

1  cubic  inch 16.39  cubic  centimeters. 

1  cubic  foot 0.02832  cubic  meter. 

1  cubic  yard 0.7645  cubic  meter. 

1  ounce 28.35  grams. 

1  pound 0.4536  kilogram. 

(14) 


HISTORY  AND  DEVELOPiMENT  OF  ARTILLERY  MATERIEL. 


In  taking  up  the  study  of  artillery,  the  student  should  know 
something  of  its  history,  the  development  of  guns  and  gun  carriages, 
and  the  reasons  for  the  various  changes  in  ordnance  materiel  which 
have  taken  place  from  time  to  time.  History  shows  that  artillery 
development  has  gone  steadily  forward.  Every  military  power  has 
striven  with  the  aid  of  its  best  engineers,  designers,  and  manufac- 
turers to  produce  a  stronger  weapon,  either  with  or  without  a  heavier 
projectile,  but  in  every  case  striving  for  greater  power. 

The  sole  use  of  a  gun  is  to  throw  a  projectile.  The  earliest  pro- 
jectile was  a  stone  thrown  by  the  hand  and  arm  of  man — either  in 
an  attack  upon  an  enemy  or  upon  a  beast  that  was  being  hunted 
for  food.  In  ancient  times  the  man  who  could  throw  the  heaviest 
stone  the  longest  distance  was  the  most  powerfully  armed.  During 
the  Biblical  battle  between  David  and  Goliath,  the  arm  of  David 
was  strengthened  by  a  leather  sling  of  a  very  simple  construction. 
Much  practice  had  given  the  youthful  shepherd  muscular  strength 
and  direction,  and  his  stronger  arm  and  straighter  aim  gave  him 
power  to  overcome  his  more  heavily  armed  adversary. 

From  the  earliest  times  man  has  felt  the  want  of  arms  that  would 
kill  at  a  distance,  and  the  ingenuity  of  the  talented  has  successively 
been  taxed  to  produce  such  weapons.  The  effect  of  a  stone  or  spear 
thrown  by  hand  so  often  proved  insufficient  that  at  once  a  desire 
arose  to  assist  the  muscles  by  the  aid  of  some  mechanical  force.  The 
sling  was  probably  the  first  weapon  used  for  hurling  missiles.  Its 
invention  is  attributed  to  the  Phoenicians  or  the  inhabitants  of  the 
Balearic  Isles,  who  were  extremely  expert  in  its  manipulation.  The 
sling  was  used  for  many  centuries  as  a  military  weapon,  and  its 
last  appearance  was  in  the  Huguenot  War  of  1572. 

The  bow  was  probably  invented  about  the  same  time  as  the  sling, 
and  for  many  centuries  was  considered  the  most  effective  offensive 
weapon  in  warfare.  Great  skill  was  attained  by  the  ancients  in  its 
use,  and  many  accounts  are  to  be  found  relative  to  the  extraordinary 
force  and  precision  with  which  an  arrow  might  be  projected.  The 
long  bow  has  always  been  the  more  universal  weapons,  the  cross- 
bow being  a  comparatively  modern  invention,  and  its  use  con- 
fined almost  entirely  to  Europe.  The  crossbow  was  extensively  used 
for  sporting  as  well  as  military  purposes,  and  it  must  have  been 
55160—21 2  (15) 


16 


a  crossbow  that  William  Tell  employed  in  his  notable  feat.     The 
Genoese  and  Gascons  were  the  most  famous  crossbow  men  in  the 

armies  of  Europe.  The 
crossbow  of  the  fourteenth 
and  fifteenth  centuries  were 
sometimes  made  with 
sights  affixed  to  them. 
Some  specimens  possessed 
a  back  sight  having  three 
or  more  peepholes,  one  over 
the  other,  which  were  evi- 
dently intended  as  guides 
for  elevation. 

Projectile-throwing  ma- 
chines were  developed  after 
the  fashion  of  a  crossbow 
mounted  upon  a  small 
wooden  carriage  which 
usually  was  a  hollowed 
trough  open  on  top  and 
upon  which  a  stone  was 
laid.  The  thong  of  the 
crossbow  was  drawn  by  a 
powerful  screw  operated  by 
man  power,  and  the  cross- 
bow- arrangement  when  released  would  throw  a  heavy  stone  quite 
a  distance.  This  was  an  attempt  by  mechanical  means  to  strengthen 
the  stroke  of  the  arm  and  increase  the  weight  of  the  projectile.  The 
Bible  states  that  King 
Usia  (809-757  B.  C.) 
placed  types  of  artillery 
on  the  walls  of  Jerusa- 
lem. The  Romans  used 
it  in  the  Punic  Wars. 
The  Alexandrian  tech- 
nicians established  sci- 
entific rules  for  the  con- 
struction of  early  weap- 
ons. Athenacus  reports 
Catapults  having  a 
range  of  656  meters  and 
that  the  gigantic  siege 
tower  at  Rhodes  successfully  resisted  stone  projectiles  weighing  176 
pounds. 

The  first  use  of  guns  or  cannon  as  a  medium  for  hurling  projectiles 
by  means  of  gunpowder  is  buried  in  obscurity ;  we  have  knowledge 


ENGLISH  ARCHER  USING  A  LONG  BOW. 


BALISTA   AND   CATAPULTA   OF   THE   GREEKS. 


17 


of  Chinese  using  a  form  of  gunpowder;  not,  however,  for  military 
parposes,  but  for  pyrotechnics,  at  a  period  long  before  the  Caucasians. 

It  is  possible  to  trace  back  the  invention  of  gunpowder  to  many 
centuries  prior  to  the  Christian  era.  Most  writers  upon  this  subject 
seem  agreed  that  it  was  known  to  the  Chinese  and  Indians,  but  the 
descriptions  given  are  so  vague  that  it  is  difficult  to  make  the 
various  accounts  coincide.  The  earliest  mention  we  have  of  gun- 
powder is  in  the  Gentoo  Laws,  where  it  is  mentioned  as  applied  to 
firearms.  This  particular  code  is  believed  to  have  been  coeval  with 
the  time  of  Moses. 

Gunpowder  has  been  known  in  India  and  China  far  beyond  all 
periods  of  investigation.  There  are  many  ancient  Indian  and 
Chinese  words  signifying  weapons  of  fire,  "heaven's  thunder," 
"devouring  fire,"  "ball  containing  terrestrial  fire,"  and  such  ex- 
pressions. 

The    ancient   Indians    made    great   use   of    explosives,   including 
gunpowder,  in  pyrotechnical  displays.    The  introduction  of  powder 
into  Europe  took  place  early 
in  the  Christian  era;  some 
believe    it   was   brought    by 
the   Moors   into   Spain   and 
others  that  it  came  through 
the  Greeks  at  Constantino- 
ple.    Both  may  be  correct, 
but   it   is  certain  that  pow- 
der   or    a   substance    closely 
akin  to  it,  was  used  at  the 
siege    of    Constantinople   in 
A.  D.  668.     The  Arabs,  or  Saracens,  are  said  to  have  used  it  in 
A.  D.  690  at  the  siege  of  Mecca. 

The  earliest  mention  of  guns  we  have  is  that  Seville  was  de- 
iVided  in  1247  by  cannon  throwing  stones;  Mibela  in  Spain,  when 
lie.-eiged  in  1259,  was  also  defended  by  a  machine  resembling  cannon; 
in  1273  Abou  Yousof  made  use  of  cannon  throwing  stone  balls  at 
the  siege  of  Sidgilmessa ;  in  1308  Ferdinand  IV  of  Castile,  at  the 
sit -<re  of  Gibraltar,  employed  guns  (or  Marquinas  de  Truenas)  ;  and 
in  1311  Ismail  attacked  Bazas,  a  town  of  Granada,  with  machines 
throwing  balls  of  fire  with  a  noise  resembling  thunder.  These  seem 
to  confirm  the  opinion  that  the  use  of  cannon  and  powder  was 
known  to  the  Arabs  or  Moors  and  introduced  by  them  into  Spain, 
from  whence  it  spread  over  Europe. 

In  the  chronicle  of  the  town  of  Ghent  for  1313  it  is  stated  that 
the  town  was  possessed  of  a  small  cannon;  and  in  the  records  of 
the  Florentine  Republic  mention  is  made  in  the  year  1325  of  two 


ARTILLERY   OF   THE   SIXTEENTH   CENTURY. 


18 

officers  being  ordered  to  manufacture  cannon  and  iron  bullets  for  , 
the  defense  of  the  castles  and  villages  belonging  to  the  Republic,  j 
The  first  German  cannon  belonged  to  the  town  of  Amberg  and 
bears  the  date  of  1301.  The  English  appear  to  have  imported 
them  from  Flanders,  for  King  Edward  III  in  1327  employed  some 
Hainaulters  who  used  them  in  his  war  with  the  Scotch.  In  1331 
cannon  were  used  by  the  King  ->f  Granada  against  Alicante,  in 
1339  at  the  siege  of  Puy-GiullortJ,  i,<\  in  the  same  year  a*  the  siege 
of  Cambray  by  Edward  II!  n  1 '3*0  by  Lequesnoy  before  Mirepoix, 
in  1345  before  Monsegur,  and  in  1346  at  Crecy;  we  have)  many 
instances  of  cannon  being  used  in  the  second  half  of  the  four- 
teenth century.  About  1350  the  North  German  knights  had  iron 
guns,  and  a  little  later  the  Free  Hanse  Towns  armed  themselves 
in  the  same  way.  In  the  year  1356  appear  large  amounts  in  the 


ITALIAN    CERBOTIAN    OF   THE    FOURTEENTH    CENTURY,    MOUNTED    ON    SEMI- 
PORTABLE   CARRIAGE. 

accounts  of  the  town  of  Nuremberg  as  having  been  spent  in  pur- 
chasing cannon  and  guns;  and  in  1365  Duke  Albert  of  Branden- 
.  -erg  defended  Einbeck  very  effectually  "  with  fire  boxes." 

The  first  records  show  that  the  Huns  used  artillery  at  the  seige  of 
v/ividale,  Italy,  in  1331.  The  material  was,  of  course,  very  crude,  and 
its  effectiveness  at  that  time  depended  largely  upon  the  smoke  and  noise 
produced.  The  barrels,  or  cannons,  in  those  days  were  constructed 
of  wood,  wrapped  with  wire  or  iron  bands,  and  the  projectiles  were 
of  stone.  These  guns  were  not  mobile  guns  in  any  sense ;  they  were 
transported  with  the  utmost  difficulty,  and  were  subject  to  capture 
by  sudden  raids  of  the  enemy. 

The  British  were  the  first  to  actually  bring  guns  out  into  field 
warfare.  They  appeared  at  the  Battle  of  Crecy  in  1346,  much 
to  the  dismay  of  the  enemy.  They  shot  anything  that  would  go 
into  the  barrels  of  the  guns,  even  bundles  of  arrows.  The  ordnance 


19 


THE  "  MONS  MEG  "  OF  EDINBURGH  CASTLE. 

(Weighing   near   4    tons,    and   shooting   a   stone    bullet    weighing 
350  pounds.) 


department  of  Edward  III  consisted  of  340  men,  with  but  12  artil- 
lerymen, showing  that  at  that  time  not  much  attention  was  paid  to 
what  is  now  an  indispensable  arm  of  the  service.  In  1415  the  num- 
bers had  increased  to  25  "  master  gunners "  and  50  "  servitour  gun- 
ners." The  gunner  was  the  gun  captain  and  had  general  charge 
stores.  In  action 
he  laid  the  piece 
and  did  the  actual 
firing. 

The  early  can- 
non of  Europe 
were  known  by 
various  names  in 
the  different  coun- 
tries. In  Italy 
they  were  known 
as  bombardes, 
probably  derived  from  "  a  bombo  et  ardore "  on  account  of  the 
great  noise  which  the  firing  of  them  occasioned.  The  French  called 
them  "  quenon  "  or  "  cannon,"  the  Germans  "  buchsen  "  or  "  boxes." 
and  the  Netherlander  "  vogheleer  "  or  "  veugliares."  Besides  these 
terms  there  were  many  others  applied  to  the  various  models,  but  it 
was  not  until  the  beginning  of  the  fifteenth  century  that  cannon  were 

classified  and  named 
according  to  their 
size.  Cannon  were  not 
adopted  or  manufac- 
tured in  France  until 
1338,  and  even  for 
many  years  after- 
wards  the  French 
looked  upon  those 
nations  who  used 
them  as  barbarians. 
The  early  cannon 

GERMAN    BREECH  LOADING    CANNON    OF    THE    SIX-        W  6  T  6         made         of 
TEENTH    CENTURY.  WTOUght,     not     Cast 

metal,  the  first  account  we  haye  of  cast  cannon  being  in  1378. 
when  a  founder  named  Aran,  at  Augsberg,  in  Germany,  cast  30  of 
a  metal  composed  of  copper  and  tin.  In  1413  Mahomed  II,  at  the 
siege  of  Constantinople,  had  an  enormous  cast  cannon.  The  bore 
is  said  to  have  been  48  inches  in  diameter  and  the  stone  bullet  to 
have  weighed  600  pounds. 


20 


21 


The  greatest  example  of  artillery  in  the  fifteenth  century  was  at 
the  siege  of  Constantinople  by  the  Turks  in  1453.  They  used  a  type 
of  mortar  that  hurled  huge  stones,  some  weighing  TOO  pounds.  Some 
of  these  guns  survived  to  engage  the  British  in  1807.  The  majority 
of  artillery  at  that  date  was  for  siege  work. 

In  the  Italian  wars  waged  by  Charles  VIII  of  France  artillery 
played  a  conspicuous  part.  However  they  lacked  the  necessary 
mobility  and  consequently  were  captured  and  recaptured  several 
times  in  a  single  engagement.  At  that,  artillery  had  done  some 
excellent  work  before  small  arms  had  attained  any  prominence. 
Although  field  artillery  was  introduced  in  the  Hussite  Wars.  1410 
to  1424,  it  was  not  until  the  Thirty  Years'  War  that  they  really  dis- 
played a  mobile  nature.  The  French  had  invented  the  limber,  and 

the  connection  between 
it  and  the  gun  trail 
was  made  with  a  rope. 
The  first  gun  that  was 
moved  by  horsepower 
was  mounted  on  an 
oblong  frame,  the  gun- 
ner sitting  directly  be- 
hind the  piece.  The 
forepart  of  the  oblong 
was  mounted  on  two 
wheels  and  the  rear 
end  was  supported  by 
the  horse  which  was 
inside  of  the  oblong 
frame.  The  majority 
of  the  guns  were  4- 

pounders.  for  as  yet  no  way  had  been,  devised  for 'the  proper  trans- 
portation of  the  heavier  guns. 

The  ancient  carriages  were  remarkable  because  of  the  fact 
that  in  general  design  they  embodied  the  same  principles  which  are 
included  in  the  field  carriages  of  to-day.  One  example  from  the 
fifteenth  century  shows  a  breech-loading  gun  mounted  in  a  cradle 
supported  by  trunnions  on  the  forward  extension  of  the  trail  over  the 
axle.  The  cradle  was  elevated  by  a  pin-and-arc  arrangement,  sup- 
ported on  the  trail.  The  axle,  supported  by  wheels,  passes  through 
the  trail  to  the  rear  of  and  below  the  cradle  trunnion  support  and  in 
front  of  the  point  of  attachment  of  the  elevating  arc. 

Field  guns  fell  into  disuse  about  1525  with  the  introduction  of 
musketry,  and  remained  so  until  1631,  when  Gustavus  Adolphus  gave 
artillery  its  true  position  on  the  battle  field. 


SOLDIER   FIRING   A    MORTAR    AND   BOMBSHELL 
REQUIRING   DOUBLE    IGNITION. 


22 


23 

Swedish  artillery  reigned  supreme  in  the  early  part  of  the  seven- 
teenth century.  Gustavus  introduced  marked  changes  by  making  the 
guns  and  the  carriages  lighter  and  handier — his  motto  was  mobility 
and  rapidity  of  fire. 

About  the  middle  of  the  eighteenth  century,  guns  were  either  24. 
12,  6,  or  3  pounders;  the  units  were  divided  into  brigades  of  4,  5, 
and  6  guns,  respectively,  and  began  to  be  separated  into  heavy  and 
light  units.  Each  field  gun  was  drawn  by  four  horses  with  a  can- 
noneer on  each  of  the  lead  horses.  The  ammunition  carried  was  100 
rounds  of  solid  shot. 


BESIEGING   A    FORTIFIED    CASTLE,   SIXTEENTH    CENTURY. 

Artillery  was  not  of  any  great  use  in  the  field  until  along  in  the 
eighteenth  century,  at  which  time  guns  were  lightened,  particularly 
so  in  France ;  powder  was  gradually  compounded  on  better  recipes, 
gun  metal  was  improved,  paper  and  linen  cartridges  were  intro- 
duced, gun  carriages  were  provided  with  an  aiming  wedge,  and 
many  new  styles  of  guns  and  mortars,  and  for  which  ammunition 
was  invented. 

Science  lent  its  aid  to  practical  men  and  not  only  exhausted 
chemical  ingenuity  in  preparing  powder  and  metal,  but  mathe- 
matical formulae  were  evolved  for  the  artilleryman,  and  the  value  of 
ricochet  firing  was  discovered. 

The  howitzer  necessary  for  high  angle  fire  put  in  its  appearance 
in  1785,  being  introduced  by  the  French  Army.  Horse  artillery 
appeared  in  the  French  Army  in  1791.  In  1800  the  horses  were 
paired  off,  with  a  driver  on  each  near  horse,  as  is  done  to-day.  In 
1808,  at  Vimera,  the  first  case  shot  came  into  use,  its  invention  being 
credited  to  an  English  colonel  by  the  name  of  Shrapnel.  It  later 


24 

became  known  as  shrapnel.  The  type  of  case  shot  used  by  Napoleon 
had  a  fuze  that  could  be  used  for  two  different  ranges.  Napoleon 
also  introduced  the  idea  of  massing  artillery  along  a  long  front. 

Field  artillery  next  began  to  appear  in  the  form  in  which  it  was 
to  retain,  with  but  a  few  changes,  until  the  era  of  the  modern  field 
carriage.  The  cradle  disappeared,  muzzle-loading  guns  cast  with 
trunnions  taking  its  place,  and  a  stepped  wedge  resting  on  the  trail 
superseded  the  pin  and  arc.  With  the  exception  of  the  gun,  most 
parts  of  these  carriages  were  of  wood,  and  remained  so  until 
1870,  when  metal  carriages  came  into  general  use.  Muzzle  loading 
guns  had  supplanted  breech-loaders  because  of  the  poor  obturation 
and  the  many  accidents  resulting  from  use  of  the  latter  type. 
Although  numerous  experiments  were  made,  breech-loading  guns 
did  not  come  into  vogue  again  until  1850,  when  the  experiments  of 
Maj.  Cavalli  (1845),  the  Walnendorff  gun  (1846),  and  the  Arm- 
strong gun  (1845)  produced  satisfactory  types. 

Between  1860  and  1870  rifling  appeared.  This  caused  sighting  to 
-be  given  greater  consideration,  as  a  rifled  gun  shoots  very  accurately. 
During  our  Civil  War  the  smoothbore  was  generally  used,  although 
rifled  guns  had  made  their  appearance  toward  the  close  of  the  con- 
flict. Direct  laying  was  the  only  method  of  fire  employed  at  this 
time. 

The  period  from  1880  to  the  present  has  brought  about  changes 
in  gun  construction  which  possibly  have  been  equaled  in  impor- 
tance to  artillery  only  by  the  present  change  which  is  taking  place 
due  to  the  development  of  motor  transportation  and  self-propel- 
ling motor  carriages.  In  this  period,  in  rapid  succession,  came 
the  modern  breech  block,  and  with  it  the  rapid-firing  gun.  This 
called  for  a  recoil  mechanism  system  to  break  the  force  of  recoil 
of  the  gun  and  restore  it  to  its  firing  position  without  seriously 
disturbing  the  lay  of  the  piece.  The  possibilities  of  rapid  and  more 
accurate  fire  were  perfected.  In  1886  came  the  invention  and  use  of 
smokeless  powder.  Previous  to  this  time  the  great  amount  of 
smoke  produced  by  the  black  powder  when  the  piece  was  fired 
retarded  the  rapidity  of  fire,  because  it  enveloped  the  materiel  in 
a  cloud  of  smoke  which  obscured  the  target  and  made  it  impossible 
to  fire  again  until  the  smoke  had  blown  away. 

The  advent  of  smokeless  powder  also  made  possible  the  selection 
of  concealed  positions.  This  in  turn  made  indirect  fire  feasible  and 
necessitated  the  development  of  better  sights.  Indirect  fire  gave  to 
the  commanders  of  firing  units  a  greater  control  over  their  fire.  With 
the  use  of  modern  recoil  mechanisms,  the  cannoneers  were  permitted 
to  serve  the  piece  continuously,  a  condition  which  was  impossible  with 


25 

the  recoiling  carriage.  Shields  were  next  introduced  on  guns  to 
protect  the  personnel  and  make  it  more  difficult  to  put  the  piece  out  of 
commission. 

The  recent  great  struggle  in  Europe  has  brought  about  conditions 
and  problems  which,  heretofore,  have  never  existed  in  warfare.  To 
meet  these,  sweeping  changes  have  been  made  in  almost  every  arm 
of  the  service,  but  probably  the  greatest  and  most  radical  change 
has  been  the  motorization  of  the  artillery. 

Heretofore,  successful  advances  by  the  troops  were  limited  to'com- 
paratively  short  distances,  due  to  the  impossibility  of  advancing 
artillery,  ammunition,  and  supplies  over  ground  which  is  often 
muddy,  full  of  shell  holes,  and  otherwise  difficult  to  travel  over 
with  enough  rapidity  to  keep  up  with  the  advancing  infantry  troops. 
The  problem  of  transporting  army  equipment  in  the  field  led  to 
the  introduction  of  tractors  and  motor  trucks. 

The  development  of  the  caterpillar  tractor  for  hauling  field  artil- 
lery, which  is  able  to  maneuver  over  almost  any  kind  of  terrain  on 
the  battle  field,  led  to  the  question  of  the  possibility  of  mounting 
guns  directly  on  a  self-propelled  vehicle  equipped  with  caterpillar 
treads.  Early  in  1918  an  8-inch  howitzer  was  mounted  on  a  self- 
propelled  carriage  and  was  fired  at  angles  of  elevation  varying  from 
i>  to  45°  with  very  satisfactory  results.  This  experimental  cater- 
pillar was  tested,  and  it  was  found  to  be  practical,  easy  to  maneuver, 
and  able  to  withstand  the  firing  strain  of  the  howitzer.  As  a  result 
of  this  test,  several  types  of  experimental  self-propelled  motor  car- 
riages have  been  manufactured,  with  armaments  varying  from  7-V 
millimeter  guns  to  240-millimeter  howitzers. 


ARTILLERY. 


Artillery  has  come  to  mean  all  firearms  not  carried  or  used  by  hand. 
excepting  machine  guns.  Artillery  is  divided  into  two  general  classi- 
fications :  Artillery  of  position  and  mobile  artillery. 

Artillery  of  position  is  that  which  is  permanently  mounted  in 
fortifications. 

Mobile  artillery  consists  of  two  classes:  First,  the  artillery  de- 
signed to  accompany  an  arm  in  the  field;  second,  railway  artillery, 
which  requires  tracks  for  its  transportation.  The  first  type  only 
is  discussed  in  this  book. 

MOBILE  ARTILLERY. 

In  designing  any  gun  intended  for  use  in  the  field,  there  are  two 
important  requirements — power  and  mobility.  Granting  that  a  gen- 
eral type  of  gun  has  been  decided  upon,  it  is  evident  that  any  in- 
crease in  either  of  these  two  factors  is  at  the  expense  of  the  other. 
It  is  necessary  to  balance  the  two,  keeping  in  mind  the  specific  pur- 
pose of  the  gun  under  consideration.  We  thus  find  it  necessary  to 
have  several  distinct  classes  of  guns,  ranging  from  the  very  power- 
ful and  almost  immobile,  to  the  very  mobile  and  comparatively 
weak.  The  general  classification  is :  Heavy  field,  light  field,  mountain 
guns  or  pack  howitzers,  trench  mortars,  and  infantry  accompanying 
guns  and  howitzers. 

Besides  the  classification,  based  upon  power,  there  is  another, 
based  upon  the  shape  of  the  trajectory.  For  the  attack  of  targets 
that  can  be  reached  by  it,  flat  trajectory  fire  is  preferred  on  account 
of  its  power  and  accuracy.  Cases  frequently  arise,  however,  where 
such  fire  is  useless,  either  the  gun  or  its  target  being  so  concealed  and 
sheltered  by  intrenchments  or  the  nature  of  the  terrain  that  higher 
angles  of  departure  and  fall  become  necessary. 

To  provide  for  both  cases,  there  are  two  or  three  types  of  weapon — 
the  long  gun  for  flat  trajectory,  the  shorter  howitzer  for  curved 
trajectory,  and  sometimes  the  still  shorter  mortar  for  high-angle 
fire.  We  thus  subdivide  our  original  classes  and  distinguish,  for 
example,  the  light  field  howitzer,  the  heavy  field  gun,  etc.  Evi- 
dently the  number  of  separate  calibers  that  might  be  adopted  to 
make  up  a  complete  series  of  types  is  very  large.  But  it  is  important 
to  reduce  this  number  to  a  minimum,  both  from  considerations  of 
economy  and  also  to  avoid  complication  in  ammunition  supplies. 

(26) 


27 

Guns  were  ordinarily  intended  for  attacking  targets  that  could  be 
reached  by  direct  fire;  that  is,  by  fire  at  angles  of  elevation  not 
exceeding  about  15°.  For  the  attack  of  targets  that  are  protected 
against  direct  fire  and  for  use  in  positions  that  are  so  sheltered  that 
direct  fire  can  not  be  utilized,  curved  fire — that  is,  fire  at  elevations 
exceeding  15° — is  necessary.  The  howitzer,  a  short  gun  designed 
to  fire  at  comparatively  large  angles  of  elevation,  is  therefore  pro- 
vided. 

Field  guns  are  now  designed  which  permit  fire  at  elevations  as 
high  as  or  higher  than  is  permitted  by  the  howitzers.  This  is  partic- 
ularly true  of  antiaircraft  guns  and  those  designed  for  use  against 
entrenched  positions.  This  development  is  an  improvement  in  the 
effectiveness  of  the  field  gun,  but  it  will  not  eliminate  the  use  of 
howitzers  of  equal  mobility,  as  the  latter  use  projectiles  of  much 
greater  weight  than  those  of  gun  materiel  of  the  same  caliber. 

The  original  American  plan  of  field  artillery  design  provided  for 
each  caliber  of  gun,  a  howitzer  of  equal  degree  of  mobility.  In  fur- 
therance of  this  idea  and  to  reduce  to  a  minimum  the  number  of 
calibers  of  mobile  artillery,  and  thus  simplify  as  far  as  possible  the 
supply  of  ammunition,  the  calibers  of  the  guns  and  howitzers  were 
so  selected  that,  while  both  guns  and  howitzers  fulfilled  the  require- 
ments as  to  weight  and  power  for  each  degree  of  mobility,  the  caliber 
of  each  was  the  same  as  that  of  the  gun  of  the  next  lower  degree  of 
mobility.  That  is,  the  howitzer  corresponding  in  mobility  to  one  of 
the  guns  is  of  the  same  caliber  as  the  next  heaviest  gun.  The  recent 
developments  in  American  artillery,  as  well  as  the  introduction  of 
artillery  of  foreign  design  into  the  American  service,  have  sustained 
this  principle. 

Under  ordinary  conditions  the  3-inch  field  gun  with  its  weight  of 
about  3.900  pounds  behind  a  six-horse  team,  is  about  as  powerful  a 
gun  as  can  follow  an  army  in  motion.  For  this  reason,  a  gun  of  ap- 
proximately this  caliber  has  been  adopted  by  most  nations  as  the 
principal  field  gun. 

The  artillery  of  all  military  powers  now  comprises  what  are  known 
as  "  rapid-fire  "  or  "  quick-firing  "  guns.  This  designation  is  too  firmly 
established  to  be  changed,  although  it  can  not  be  considered  as  accu- 
rately descriptive  since  rapidity  of  fire  is  characteristic  of  nearly  all 
modern  types.  The  real  distinguishing  mark  of  a  rapid-fire  gun  is 
that  its  carriage  does  not  move  materially  in  firing ;  instead,  the  gun 
recoils  on  the  carriage  and  is  returned  to  the  firing  position  by  springs 
or  their  equivalent.  There  are  a  number  of  other  features,  some  of 
which  are  found  in  all  rapid-fire  models;  but  these  are  of  secondary 
significance  and  either  old  ideas  which  could  not  be  worked  out 
practically  before  the  development  of  the  gun-recoil  carriage  or  else 
improvements  developed  since  in  the  effort  to  get  the  best  results  out 


28 

of  it.  For  example,  it  is  useless  to  attach  shields  to  a  rigid  carriage, 
for,  since  the  cannoneers  have  to  stand  clear  to  avoid  the  recoil,  they 
can  not  take  advantage  of  them.  Mechanism  for  traversing  the 
piece  on  its  carriage  is  unnecessary  with  the  rigid  system,  but  be- 
comes necessary  as  soon  as  we  adopt  a  carriage  that  remains  more  or 
less  firmly  anchored  to  the  ground.  Fixed  ammunition  and  instru- 
ments for  indirect  laying  are  not  essentially  a  part  of  either  a  rigid  or 
a  gun-recoil  system:  they  are  sometimes  used  with  the  former  and 
occasionally,  but  rarely,  omitted  from  the  latter ;  but  they  have  their 
full  value  only  in  rapid-fire  material. 

Our  mobile  artillery  is  divided  into  the  following  classes: 
(a)   Divisional  artillery;   such  as,  the  3-inch   and  75-millimeter 
guns  and  105-millimeter  howitzers.     (The  155-millimeter  howit/i-r 
to  be  used  as  a  substitute.) 

(?>)  Corps  artillery;  such  as,  the  4.7-inch  guns  and  155-millimeter 
howitzers. 

(c)  Army  artillery;  such  as.  the  155-millimeter  guns,  8-inch  and 
240-millimeter  howitzers.    Any  caliber  may,  if  required,  be  assigned 
to  army  artillery. 

(d)  Mountain  or  pack  materiel  transported  on  the  backs  of  mules. 
For  mountain  service  the  system  composed  of  gun  and  carriage  must 
be  capable  of  rapid  dismantling  into  parts,  none  of  which  forms  too 
heavy  a  load  for  a  pack  mule.    The  weight  of  the  load  including  the 
saddle  and  equipment  should  not  exceed  350  pounds.    The  mountain 
gun  in  our  service  is  the  2.95-inch. 

(e)  Infantry  accompanying  guns;  such  as,  the  37-millimeter. 
(/)  Trench  mortars. 

Carriages  are  designed  to  function  in  a  certain  way  and  are  not 
temperamental.  They  follow  absolutely  and  certainly  fixed  mechan- 
ical laws.  If  they  fail  rtere  is  always  a  reason  which  can  be 
remedied.  Certain  parts  are  jgiven  certain  shapes  and  forms,  and  are 
machined  to  fine  adjustments;\herefore  in  taking  down  and  assem- 
bling artillery  materiel  brains  £*id  dexterity  are  the  tools  to  use 
rather  than  force  and  sledge  hammers.  Treat  these  guns  as  you 
would  a  friend  whom  you  know  you  can  depend  on.  They  will  not 
fail  you. 


CANNONS. 


THEIR  FUNCTIONS  AND  CONSTRUCTION. 

"A  cannon  is  a  machine  by  which  the  force  of  expanding  gas  is 
used  for  the  purpose  of  propelling  a  projectile  in  a  definite  direction.'* 

A  cannon  consists  of  a  metal  tube,  closed  at  one  end,  and  of  suffi- 
cient strength  to  resist  the  pressure  of  the  gases  of  explosion.  The 
force  of  the  expanding  gases  acting  on  the  base  of  a  projectile 
placed  in  the  cannon  causes  it  to  start  on  its  flight.  When  the  charge 
is  ignited,  the  explosion  or  rapid  combustion  of  the  powder  gives  rise 
to  a  large  amount  of  gas,  which  tends  to  expand  and  to  occupy  a 
space  greater  than  that  in  which  the  powder  was  originally  con- 
tained; consequently,  it  exerts  a  pressure  in  all  directions,  and  the 
energy  developed  is  utilized  in  forcing  the  projectile  from  the  tube. 
The  major  portion  of  the  energy  is  distributed  as  follows : 

(a)  Energy  of  translation  of  the  projectile. 

(ft)   Energy  of  rotation  of  the  projectile. 

(c)  Energy  of  translation,  in  recoil,  of  the  gun. 

(d)  Energy  of  translation  of  the  unburnt  charge  and  gases. 

(e)  Energy  consumed  in  overcoming  the  passive  resistance  of  the 
projectile.     This  resistance  arises  from  the  friction  of  the  projectile 
against  the  walls  of  the  bore,  and  of  the  rotating  band  against  the 
driving  edges  of  the  lands.    In  the  first  stages,  it  also  arises  from  the 
cutting  of  grooves  in  the  rotating  band  by  the  lands. 

The  balance  of  the  energy  is  expended  by  being  lost  as  heat  to  the 
gun  and  that  which  remains  in  the  gas  as  sensible  or  latent  heat. 

In  the  cannon,  the  space  in  which  the  powder  is  burning  has  a 
fixed  capacity  until  sufficient  force  has  been  developed  to  start  the 
projectile.  When  the  projectile  begins  to  move,  the  capacity  of  the 
gas  container  begins  to  increase,  and  this  increase  tends  to  decrease 
the  expansive  force  of  the  gas.  Thus  the  progressive  explosion  of 
the  powder,  by  increasing  the  amount  of  gas  in  the  container,  is 
increasing  the  expansive  force,  while  at  the  same  time  the  increase 
in  the  size  of  the  container  is  decreasing  the  expansive  force.  If  the 
effects  of  these  two  opposing  factors  could  be  maintained  equal  in 
value  from  the  time  the  projectile  starts  to  move  until  it  leaves  the 
muzzle  of  the  cannon,  it  would  then  be  possible  so  to  regulate  the 
powder  charge  that  the  force  developed  would  rise  to  the  maximum 
pressure  safe  for  the  cannon  when  the  projectile  starts  to  move,  and 
would  then  remain  constant  until  the  projectile  leaves  the  muzzle. 
This  would  be  the  ideal  progressive  explosion,  for  since  the  maximum 

(29) 


30 

allowable  pressure  would  be  exerted  upon  the  projectile  during  its 
entire  path  while  in  the  bore,  the  maximum  possible  initial  velocity 
for  the  projectile  and  cannon  considered  would  be  developed. 

A  cannon  may  be  considered  as  a  tube  destined  to  withstand  a 
given  pressure  from  within,  throwing  a  projectile  which  shall  pro- 
duce certain  effects  at  given  distances.  In  constructing  such  a  tube 
we  must  first  consider  what  pressures  it  will  have  to  withstand  at 
the  various  points  of  its  length,  and  then  make  it  strong  enough  to 
insure  perfect  safety.  Not  only  must  the  gun  be  sufficiently  strong, 
but  it  must  not  be  too  heavy;  so  it  is  important  that  the  material 
shall  be  arranged  in  such  a  manner  that  there  may  be  no  waste  of 
its  strength — in  fact,  so  arranged  that  every  part  shall  perform  its 
own  share  in  withstanding  the  pressure  from  within.  Shortly  after 
the  shot  begins  to  move  the  pressure  inside  the  gun  decreases,  and 
continues  to  decrease  as  the  projectile  approaches  the  muzzle;  for 
this  reason  the  piece  is  made  stronger  at  the  powder  chamber  than 
toward  the  muzzle  end. 

Looking  simply  to  the  construction  of  a  gun  cylinder,  we  find  that 
the  two  principal  stresses  to  which  such  a  cylinder  is  subjected  upon 
the  explosion  of  a  charge  are,  first,  a  circumferential  or  tangential 
stress  or  tension,  coupled  with  a  radial  stress,  tending  to  split  the 
gun  open  longitudinally;  second,  a  longitudinal  stress  tending  to 
pull  the  gun  apart  in  the  direction  of  its  length. 

It  may  be  readily  understood  that  during  the  travel  of  the  pro- 
jectile through  the  bore  of  the  gun,  from  the  instant  of  ignition  of  the 
charge  until  it  has  left  the  muzzle,  tremendous  stresses  are  set  up 
in  the  tube.  In  the  earlier  days  of  ordnance  construction  these 
stresses  were  met  by  sheer  weight  of  metal,  but  as  the  weight  of 
projectiles  increased,  with  consequent  increase  in  powder  charges, 
this  weight  of  metal  became  so  great  as  to  impede  the  desired  mo- 
bility of  the  material.  Consequently  forgings  of  refined  and  alloyed 
steels  took  the  place  of  the  castings  or  forgings  of  iron  or  simple 
steels. 

As  explosives  increased  in  power  the  plain  tube,  even  though  built 
of  alloyed  steels,  became  incapable  of  containing  the  chamber  pres- 
sures, even  though  of  excessive  weight.  This  problem  was  finally 
met  through  the  construction  of  built-up  and  wire- wrapped  guns. 

A  built-up  gun  is  one  in  which  the  principal  parts  are  separately 
constructed  and  then  united  in  a  peculiar  manner;  and  guns  so  con- 
structed may  be  composed  of  different  kinds  of  metal  or  of  the  same 
kind  of  metal  throughout. 

On  the  wire-wound  gun  the  wire  is  wound  in  layers  around  an 
inner  tube  of  steel.  Each  layer  is  wound  with  a  tension  on  the 
wire,  and  each  exerts  a  compression  on  the  layer  which  is  beneath  it. 


31 

The  result  is  that  when  completed  the  outer  layers  are  in  extension, 
gradually  diminishing  to  the  inner  layers,  which  are  in  compression, 
all  within  the  elastic  limit. 

RIFLING  consists  of  a  number  of  helical  grooves  cut  in  the  sur- 
face of  the  bore.  The  soft  metal  of  the  rotating  band  of  the  projec- 
tile is  forced  into  these  grooves  and  causes  the  projectile  to  take  up 
the  motion  of  rotation  as  it  passes  through  the  bore. 

Rotation  of  the  projectile  around  its  longer  axis  is  necessary  for 
stability  in  flight.  By  twist  of  rifling  is  meant  the  inclination  of  one 
of  the  grooves  to  the  element  of  the  bore  at  any  point.  Rifling  is  of 
two  kinds : 

(a)  Uniform  twist,  or  that  in  which  the  twist  is  constant  through- 
out the  bore. 

(£>)  Increasing  twist,  or  that  in  which  the  twist  increases  from 
the  breech  toward  the  muzzle  end  of  the  bore. 

The  object  of  rifling  is  to  impart  to  the  shell  a  rapid  rotation 
about  its  axis  and  thus  give  it  the  powers  of  a  gyroscope.  These 
powers  resist  any  deflection  of  the  shell's  longitudinal  axis.  If  it 
were  not  thus  given  gyroscopic  properties,  with  great  power  to 
resist  deflecting  influences,  inaccuracies  would  result. 

Rotation  is  obtained  by  rifling  in  the  bore  of  the  gun  and  a  soft 
metal  (copper)  rotating  band  on  the  body  of  the  shell.  This  band 
is  forced  into  the  grooves  as  soon  as  the  shell  starts  from  the  origin 
of  rifling.  The  rotating  band  follows  the  grooves,  and  as  these  are 
spiral,  the  shell  is  rotated  as  it  travels  the  bore. 

The  grooves  of  rifling  are  spirals.  The  pitch  of  the  rifling,  or 
the  inclination  of  grooves  to  axis  of  bore,  is  called  twist.  It  is 
usually  designated  by  one  turn  in  so  many  calibers.  With  uniform 
twist  the  projectile  must  take  its  rotation  the  instant  it  starts,  whereas 
with  increasing  twist  the  rotation  may  be  impaired  gradually.  With 
increasing  twist  there  appears  the  disadvantage  that  on  account  of  the 
constantly  changing  angle  it  is  hard  to  preserve  gas  tightness  be- 
tween the  rotating  band  and  the  grooves. 

A  rifled  cannon  is  so  called  on  account  of  the  spiral  grooves  which 
are  cut  into  the  surface  of  the  bore,  and  into  which  the  soft  metal 
of  the  rotating  band  on  the  projectile  is  forced,  thus  imparting  to 
the  projectile  a  motion  of  rotation.  The  spaces  between  grooves 
are  called  lands. 

The  caliber  of  a  gun  is  the  diameter  across  the  tops  of  the  opposite 
lands.  The  bore  is  the  cylindrical  hole  in  the  gun  extending  from 
breech  face  to  muzzle  face  of  the  tube.  That  part  of  the  bore  from 
the  breech  plug,  when  closed,  to  the  point  where  rifling  begins  is 
called  the  powder  chamber.  Its  capacity  is  the  total  cubical  contents 
from  plug  face  to  base  of  projectile,  when  the  latter  is  "  seated  "  in 

55160—21 3 


32 

position  for  firing.  The  rear  part  of  the  chamber  is  cylindrical 
for  some  distance.  This  cylinder  merges  into  "the  slope  of  the 
powder  chamber,"  an  easy  slope,  which  in  turn  merges  into  the  "  com- 
pression slope,"  which  ends  in  the  "seat  of  rifling";  that  is,  the 
rear  end  of  the  rifled  cylinder.  When  a  shell  is  in  position  for  firing, 
its  rotating  band  takes  the  seat  of  rifling. 

Initial  velocity. — By  initial  or  muzzle  velocity  is  meant  the  rate 
of  travel  in  feet  per  second  at  which  a  projectile  leaves  the  muzzle 
of  a  cannon.  In  its  application  to  practical  problems,  however,  we 
usually  take  as  the  initial  velocity  the  maximum  velocity  attained  by 
the  projectile.  This  is  acquired,  not  strictly  at  the  muzzle,  but  a 
short  distance  beyond  it ;  for  so  long  as  the  projectile  is  in  the  powder 
blast  the  force  of  the  expanding  gases  continues  to  a  limited  extent 
to  act  upon  it,  and  so  long  as  this  force  is  greater  than  the  retarding 
force  of  the  air,  the  velocity  of  the  projectile  is  increased. 

Density  of  loading. — The  density  of  loading  is  the  ratio  of  the 
weight  of  the  powder  charge  to  the  weight  of  a  volume  .of  distilled 
water,  at  the  temperature  of  maximum  density,  that  will  fill  the 
powder  chamber. 

This  ratio  expresses  the  weight  of  powder  per  unit  volume  of  the 
powder  chamber,  in  terms  of  the  weight  of  a  unit  volume  of  water. 
The  force  developed  by  the  explosion  of  powder  in  a  container  de- 
pends both  upon  the  amount  of  powder  and  upon  the  size  of  the 
container;  that  is,  it  depends  upon  the  amount  of  powder  per  unit 
volume  of  the  container,  or  in  other  words  upon  the  density  of  load- 
ing. The  density  of  loading,  therefore,  has  a  direct  and  important 
bearing  upon  the  initial  velocity,  and  in  order  that  it  may  be  deter- 
minable  and  constant  in  practice  under  any  given  set  of  conditions, 
it  is  important  to  keep  constant  the  size  of  the  container.  It  is  con- 
sequently essential  that  projectiles  always  be  well  seated,  so  that  in 
any  particular  piece,  the  base  will  always  be  the  same  distance  from 
the  face  of  the  breech. 

Ignition,  inflammation  and  combustion. — By  ignition  is  meant 
setting  fire  to  the  charge ;  by  inflammation,  the  spread  of  flame  over 
the  surface  of  each  grain  and  from  grain  to  grain  of  the  charge; 
and  by  combustion,  the  burning  of  the  inflammed  grain  from  the 
surface  of  ignition  inward,  or  outward,  or  both,  according  to  the 
form  of  the  grain.  It  is  desirable  to  produce  as  nearly  as  possible 
a  simultaneous  ignition  of  all  the  powder  grains  of  the  charge,  in 
order  that  inflammation  and  combustion  be  as  nearly  uniform  as 
possible,  thus  eliminating  variations  in  the  rate  of  emission  of  gas 
and  consequent  differences  in  force  developed  at  any  elapsed  time 
a"ter  the  first  particle  of  a  charge  has  been  ignited.  For  this  reason, 
in  the  larger  charges  an  igniting  charge  of  black  powder  is  attached 
to  each  end  of  each  section  of  a  powder  charge,  and  a  core  of  black 


33 

powder  is  extended  from  end  to  end  as  well.  In  the  smaller  charges, 
the  igniting  charge  is  attached  to  one  end  only  of  the  propelling 
charge,  and  the  core  is  omitted. 

Size  and  shape  of  the  powder  grain. — The  force  or  pressure  de- 
veloped at  any  instant  of  an  explosion  depends  upon  the  amount  of 
gas  that  has  been  evolved.  This  depends  upon  the  rate  of  combus- 
tion, and  the  area  of  the  burning  surface.  Therefore  the  size  and 
shape  of  the  grain  have  an  important  bearing  upon  the  initial 
velocity. 

As  a  rule,  the  larger  the  grain  the  less  will  be  the  area  of  burning 
surface  per  pound  of  powder,  and  the  slower  will  be  the  rate  of 
emission  of  gas  for  the  same  rate  of  burning  for  any  given  charge. 
The  rate  of  production  of  gas  at  any  instant  depends  upon  the 
area  of  the  burning  surface  at  that  instant,  which,  in  turn  depends  not 
only  upon  the  size  but  also  upon  the  shape  of  the  grain.  Any  change 
in  this  area  as  combustion  progresses  produces  a  corresponding 
change  in  the  rate.  In  a  nonperf orated  grain  of  any  shape,  as  the 
outer  layers  are  consumed,  the  area  of  burning  surface  decreases,  thus 
tending  to  decrease  the  rate  of  gas  production.  This  decrease,  com- 
bined with  the  increase  in  size  of  container  after  the  projectile  starts 
to  move,  will  cause  the  pressure  to  start  decreasing  after  having 
reached  a  maximum,  thus  allowing  the  initial  velocity  to  fall  below 
that  which  would  be  attained  could  the  pressure  be  maintained  at  its 
maximum.  Hence,  to  keep  .the  burning  surface  from  decreasing, 
perforated  grains  are  employed,  which  are  consumed  by  combustion 
progressing  outward  from  the  inner  surfaces  of  the  perforations, 
as  well  as  inward  from  the  exterior  surfaces  of  the  grain.  Thus 
while  the  exterior  burning  surfaces  are  decreasing  as  combustion 
progresses,  the  surfaces  of  the  perforations  are  increasing,  and  the 
total  burning  surface  is  maintained  nearly  constant.  In  this  way 
the  maximum  explosive  effect  is  more  nearly  approached. 

A  BREECH  MECHANISM,  or  fermeture,  is  a  mechanical  device 
for  closing  the  rear  end  of  the  chamber  or  bore  of  a  breech-loading 
gun.  The  term  includes  the  breechblock  or  plug,  all  mechanism 
contained  in  or  with  it,  and  the  necessary  operating  gear.  The  fol- 
lowing may  be  said  to  be  the  principal  requirements  for  a  successful 
breech  mechanism : 

Safety, 

Ease  and  rapidity  of  working, 

Not  easily  put  out  of  order, 

Ease  of  repair, 

Inter  changeability. 

The  breech  mechanism  comprises  the  breechblock,  the  firing 
mechanism,  and  the  mechanism  for  the  insertion  and  withdrawal 
of  the  block.  There  are  two  general  methods  of  closing  the  breech. 
In  the  first  method  the  block  is  inserted  from  the  rear.  The  block 


34 

is  provided  with  screw  threads  on  its  outer  surface  which  engage 
in  corresponding  threads  in  the  breech  of  the  gun.  In  order  to 
facilitate  insertion  and  withdrawal  of  the  block  the  threads  on  the 
block  and  breech  are  interrupted.  The  surface  of  the  block  is 
divided  into  an  even  number  of  sectors,  and  the  threads  of  the 
alternate  sectors  are  cut  away.  Similarly,  the  threads  in  the  breech 
are  cut  away  from  those  sectors  opposite  the  threaded  sectors  on 
the  block.  The  block  may  then  be  rapidly  inserted  nearly  to  its 
seat  in  the  gun,  and  when  turned  through  a  comparatively  small 
arc,  say  one-eighth  or  one-twelfth  of  a  circle,  depending  upon  the 
number  of  sectors  into  which  the  block  is  divided,  the  threads  on  the 
block  and  in  the  breech  are  fully  engaged  and  the  block  is  locked. 

In  the  second  method  a  wedge-shaped  block  is  seated  in  a  slot 
cut  in  the  breech  of  the  gun  at  right  angles  to  the  bore,  and  slides 
in  the  slot  to  close  or  open  the  breech. 

Variations  of  these  two  methods  will  be  noted  in  the  detailed 
descriptions  of  the  guns  which  follow. 

The  most  notable  variation  from  the  above  two  types  is  the  Nor- 
denfeld  type  of  breech  mechanism,  a  rotating  block  construction 
found  on  the  French  37-millimeter  and  75-millimeter  guns,  de- 
scribed more  fully  and  illustrated  in  the  description  of  these  guns. 

The  breechblock  is  usually  supported  in  the  jacket  of  the  gun  or 
in  a  breech  ring  screwed  into  the  jacket.  The  seat  in  the  jacket 
being  of  greater  diameter  than  could  be  provided  in  the  tube,  the 
bearing  surface  of  the  screw  threads  on  the  block  is  increased  and 
the  length  of  the  block  may  be  diminished. 

The  slotted  screw  breechblock  is  used  to  a  great  extent  in  our 
service.  Its  advantages  are  uniform  distribution  in  the  gun  of  the 
longitudinal  stress  produced  by  the  powder  pressure  and  lightness 
permitted  in  the  construction  of  the  breech  end  of  the  gun.  In  the 
model  of  1917,  3-inch  antiaircraft  gun,  however,  and  in  the  Ameri- 
can 75-millimeter  gun,  the  sliding  block  operating  vertically  has  been 
adopted  for  the  reason  that  it  permits  of  simpler  mechanism  for 
semiautomatic  operations. 

INTERIOR  BALLISTICS  treats  of  the  motion  of  the  projec- 
tile while  still  in  the  bore  of  the  gun.  It  includes  the  study  of  the 
mode  of  combustion  of  the  powder,  the  pressure  developed,  and  the 
velocity  of  the  projectile  along  the  bore  of  the  gun. 


MOUNTS  FOR  MOBILE  ARTILLERY. 


A  modern  gun  carriage  is  expected  to  stand  steady  on  firing,  so 
that  in  the  first  place  it  requires  no  running  up,  and  in  the  second 
place  it  maintains  the  direction  of  the  gun  so  that  only  a  slight  cor- 
rection in  elevation  and  direction  is  required  after  each  round.  The 
carriage  is  maintained  in  position  by  the  spade,  which  sinks  into  the 
ground,  and  by  the  friction  of  the  wheels  upon  the  ground.  If  the 
force  of  the  recoiling  gun  were  communicated  directly  to  the  anchored 
carriage  the  effect  would  be  to  make  it  jump  violently,  which  would 
not  only  disturb  the  lay,  but  would  prevent  the  cannoneers  from 
maintaining  their  position.  The  hydraulic  recoil  brake  is  therefore 
interposed  between  gun  and  carriage. 

If  the  gun  were  rigidly  attached  to  the  carriage,  the  latter  would 
be  forced  back  a  short  distance  at  each  round,  and  the  whole  of  the 
recoil  energy  would  have  to  be  absorbed  in  that  short  motion.  In- 
stead of  this,  the  gun  alone  is  allowed  to  recoil  several  feet  on  the 
carriage  and  although  the  recoil  energy  is  in  this  case  greater  than 
it  would  be  if  gun  and  carriage  recoiled  together,  yet  it  is  so  grad- 
ually communicated  to  the  carriage  that  instead  of  a  violent  jerk 
we  have  a  steady,  uniform  pull,  the  only  effect  of  which  is  to  slightly 
compress  the  earth  behind  the  spade.  In  a  well-designed  carriage 
the  amount  of  this  pull  should  not  greatly  exceed  that  required  to  lift 
the  wheels  off  the  ground  by  rotating  the  carriage  about  the  spade 
and  must  be  less  if  complete  stability  is  required. 

The  only  motion  of  the  carriage  which  takes  place  is  that  due  to 
the  elastic  bending  and  rebound  of  its  parts  under  the  strain  set  up 
in  discharge.  These  strains  are  inevitable  since  the  direction  of  re- 
coil can  not  be  always  exactly  in  the  line  of  the  resistance  of  the 
earth  behind  the  spade.  This  movement  of  the  axis  is  known  as 
"  jump  "  and  must  be  determined  by  experiment  for  the  individual 
piece  in  its  particular  mounting  as  it  is  affected  by  many  features  of 
construction. 

The  principal  parts  of  the  typical  gun  carriage  are  the  recuperator ; 
the  top  carriage;  the  trail;  the  wheels  and  axle.  The  gun  slides  in 
recoil  on  the  upper  surface  of  the  recuperator  which  contains  the 
recoil  controlling  parts. 

In  the  design  of  the  carriage  the  constructional  difficulty  lies  not 
so  much  in  preventing  the  carriage  from  recoiling,  but  in  preventing 

(85) 


36 

the  wheels  from  rising  off  the  ground  at  the  shock  of  discharge. 
The  force  of  the  recoil  of  the  gun  tends  to  turn  the  carriage 
over  backwards  about  the  point  of  the  trail  or  center  of  the  spade. 
This  force  is  resisted  by  the  weight  of  the  gun  and  carriage,  which 
tends  to  keep  the  wheels  on  the  ground.  The  leverage  with  which 
the  overturning  force  acts  varies  with  the  distance  of  its  line  of 
action  above  the  center  of  pressure  on  the  spade;  the  leverage  with 
which  the  restraining  force  acts  varies  with  the  horizontal  distance 
of  the  center  of  gravity  of  the  gun  and  carriage  from  the  center  of 
pressure  on  the  float. 

It  follows  that  the  steadiness  of  the  carriage  for  a  given  muzzle 
energy  may  be  promoted  by  four  factors : 

(a)  Increasing  the  weight  of  the  gun  and  recoiling  parts.  This 
reduces  the  energy  of  recoil. 

(&)  Increasing  the  length  of  recoil  allowed.  This  reduces  the 
overturning  pull. 

(<?)  Keeping  the  gun  as  low  as  possible,  either  by  reducing  the 
height  of  the  wheels  or  by  cranking  the  axle  downwards.  This 
reduces  the  leverage  of  the  overturning  force. 

(d)  Increasing  the  length  of  the  trail.  This  increases  the  lever- 
age of  the  steadying  force. 

The  well-designed  gun  carriage  is  one  that  combines  these  factors 
in  a  practical  way,  so  as  to  give  the  greatest  possible  stability  to 
the  carriage,  at  the  same  time  keeping  within  the  limits  of  weight 
imposed  by  the  necessity  of  mobility. 

Gun  carriages  are  so  constructed  as  to  permit  movement  of  the 
piece  in  either  a  vertical  or  horizontal  plane.  These  motions  may 
be  simultaneous  if  so  desired,  and  by  a  proper  combination  of  the 
two  motions,  the  axis  of  a  gun  may  be  aligned  in  any  desired  direc- 
tion within  the  limits  of  motion  of  its  mount.  The  two  kinds  of 
motion  are  designated  as  follows:  Rotation  of  the  piece  about  a 
vertical  axis,  its  inclination  with  the  horizontal  remaining  un- 
changed, is  called  "  traversing  " ;  movement  of  the  piece  in  a  vertical 
plane,  the  horizontal  projection  of  the  axis  of  its  bore  remaining 
unchanged,  is  called  "  elevating." 

Gun  carriages  are  provided  with  mechanisms  for  giving  the  pieces 
accurately  controlled  motion  in  both  azimuth  and  elevation.  Two 
types  of  elevating  mechanisms  are"  in  common  use.  The  first  is  the 
telescopic  screw.  This  gives  a  considerable  length  of  screw  for  a 
short  assembled  length  and  permits  rapidity  of  action  (since  the 
movement  of  the  inner  screw  is  equal  to  the  sum  of  the  pitches  of 
the  outer  and  inner  screw  for  each  turn  of  the  pinion),  combined 
with  the  nicety  of  adjustment  of  a  single  screw  of  fine  pitch. 

In  the  second  type,  the  motion  is  communicated  to  rockers  at- 
tached to  the  bottom  of  the  cradle,  through  the  engagement  of 
worms  or  pinions,  with  teeth  cut  on  the  circumference  of  the  rockers. 


37 

This  method  is  in  use  on  all  howitzers  and  a  great  many  guns. 
It  allows  for  a  very  high  angle  of  elevation,  and  when  fitted  with  a 
quick-loading  gear,  allows  for  the  rapid  placing  of  the  piece  in  load- 
ing position  after  firing. 

Movement  of  the  gun  in  azimuth  is  accomplished  in  several  ways ; 
one  is  to  pivot  the  cradle  of  the  gun  in  a  saddle  which  itself  pivots 
on  a  horizontal  transom  of  the  trail.  Another  is  to  mount  the  gun 
and  elevating  gear  on  some  form  of  top  carriage,  and  pivot  this 
top  carriage  over  the  axle.  Still  another  is  to  traverse  the  whole 
piece  along  the  axle,  pivoting  on  the  spade.  This  is  a  method  used 
by  the  French  in  some  of  their  designs.  It  has  the  disadvantage  of 
allowing  only  for  a  small  angle  of  traverse. 

The  above  principles  of  design  are,  of  course,  modified  consider- 
ably in  the  case  of  semipermanent  mounts  which  fire  from  platforms 
and  for  antiaircraft  guns  which  have  special  mountings  suited  to 
their  special  use. 


RECOIL  MECHANISMS. 


RECOIL  BRAKES  AND  METHODS  OF  COUNTERRECOIL. 

The  stresses  to  which  a  gun  carriage  is  subjected  are  due  to  the 
action  of  the  expanding  powder  gases  on  the  piece.  Gun  carriages 
are  constructed  either  to  hold  the  piece  without  recoil  or  to  limit  the 
recoil  to  a  certain  convenient  length.  In  the  first  case  the  maxi- 
mum stress  on  the  carriage  is  readily  deduced  from  the  maximum 
pressure  in  the  gun.  In  the  second  case  it  becomes  necessary  to 
determine  all  the  circumstances  of  recoil  in  order  that  the  force 
acting  at  each  instant  may  be  known  and  the  parts  of  the  carriage 
designed  to  withstand  this  force  and  to  absorb  the  recoil  in  the 
desired  length. 

Assume  the  gun  to  be  so  mounted  that  it  may  recoil  horizontally 
and  without  resistance.  On  explosion  of  the  charge,  the  parts  of 
the  system  acted  upon  by  the  powder  gases  are:  the  gun,  the  pro- 
jectile, and  the  powder  charge  itself,  the  latter  including  at  any 
instant  both  the  unburned  and  the  gaseous  portion.  While  the  pro- 
jectile is  in  the  bore,  if  we  neglect  the  resistance  of  the  air,  none  of 
the  energy  of  the  powder  gases  is  expended  outside  the  system. 
The  center  of  gravity  of  the  system  is  therefore  fixed  and  the  sum  of 
the  quantities  of  motion  in  the  different  parts  is  zero.  The  move- 
ment of  the  powder  gases  will  be  principally  in  the  direction  of  the 
projectile.  The  weight  of  the  gun,  projectile,  and  charge  being 
known,  the  complete  relations  between  the  velocity,  time,  and  length 
of  free  recoil  may  be  established  by  formula. 

Thus  far  we  have  neglected  all  resistances  and  have  considered 
the  movement  of  the  gun  in  recoil  as  unopposed.  However,  when 
the  gun  is  mounted  on  a  carriage  the  recoil  brakes,  of  whatever 
character,  begin  to  act  as  soon  as  .recoil  begins,  and  consequently 
the  velocity  of  recoil  is  less  at  each  instant  of  travel  than  when 
unopposed.  It  is  evident  that  the  higher  the  resistance  offered  by 
the  recoil  brakes  the  shorter  will  be  the  total  length  of  recoil.  A 
little  consideration  will  show  that  if  the  total  resistance  to  recoil  is 
made  constant  throughout,  its  value  will  be  less  than  the  maximum 
value  of  a  variable  total  resistance  which  will  stop  the  gun  in  the 
same  length  of  recoil.  For  a  given  length  of  recoil,  the  constant 
resistance  will  therefore  produce  less  strain  in  the  carriage,  and  for 
this  reason  is  usually  adopted,  except  where  stability  can  be  increased 
by  using  a  variable  pull. 

(38) 


39 


P' 


FIG.  A. 


The  recoil  system  of  a  gun  carriage  consists  of  a  recoil  brake  for 
controlling  the  recoil  and  limiting  its  length,  a  counterrecoil  mech- 
anism for  returning  the  gun  to  the  firing  position  and  keeping  it 
there,  and  a  counterrecoil  brake  or  buffer  to  soften  the  shock  as 
the  gun  runs  into  the  firing  position. 

Recoil  brakes  of  the  friction  type  were  formerly  used.  Pneumatic 
brakes  were  also  used  to  some  extent.  Both  of  these  types  have  now 
been  entirely  superseded  by  the  hydraulic  recoil  brake. 

A  hydraulic  recoil  brake  consists  of  a  cylinder,  filled  with  liquid, 
and  a  piston.  Relative  movement  is  given  to  the  cylinder  and  piston 
by  the  recoil,  and  provision  is  made 
for  the  passage  of  the  liquid  from 
one  side  of  the  head  of  the  piston 
to  the  other,  by  apertures  cut  into 
the  piston  or  in  the  walls  of  the 
cylinder.  The  power  of  the  brake 
lies  in  the  pressure  produced  in  the  cylinder  by  the  resistance 
offered  by  the  liquid  to  motion  through  the  apertures.  If  the  area 
of  the  apertures  is  constant,  it  is  evident  that  the  resistance  to 
flow  will  be  greater  as  the  velocity  of  the  piston  or  the  velocity  of 
recoil  is  greater.  Therefore,  the  pressure  in  the  cylinder,  which  meas- 
ures the  hydraulic  resistance  offered,  will  vary  with  the  different 
values  of  the  velocity  of  recoil.  If,  however,  the  apertures  are  con- 
structed in  such  a  manner  that  the  area  of  aperture  increases  when 

the  velocity  of  the  piston  increases, 
and  diminishes  when  that  velocity  di- 
minishes, the  variation  in  the  area  of 
aperture  may  be  so  regulated  that  the 
pressure  in  the  cylinder  will  be  con- 
stant, or  will  vary  in  such  a  manner 
as  to  keep  the  total  resistance  to  recoil  constant,  or  it  may  be  made 
to  vary  in  any  manner  desired. 

In  figure  A  is  shown  one  type  of  hydraulic  brake.  It  consists  of 
a  cylinder  on  the  inner  surface  of  which  are  formed  bars  of  vary- 
ing cross  sections,  called  throttling  bars  (T),  piston  (p),  and 
piston  rod.  Either  the  piston  rod  is  secured  to  the  carriage,  the 
cylinder  moving  to  the  rear  with  the  gun,  or  the  cylinder  is  secured 
to  the  carriage,  the  piston  moving  to  the  rear  with  the  gun. 

Through  the  piston  head  are  cut  slots  or  apertures  through  which 
the  liquid  is  forced  from  one  side  of  the  piston  to  the  other  as  the 
cylinder  or  piston  moves  in  recoil.  Each  slot  has  the  dimensions 
of  the  maximum  section  of  the  throttling  bar  with  just  enough  clear- 
ance to  permit  operation.  The  area  of  orifice  open  for  the  flow  of 
liquid  at  any  position  of  the  piston  is  therefore  equal  to  the  area  of 


~7     FF 


-P 


FIG.  B. 


40 

the  slots  minus  the  area  of  cross  section  of  the  throttling  bar,  and 
is  so  determined  that  the  resistance  to  the  flow  of  the  liquid,  or  the 
pressure  in  the  cylinder,  is  made  constant  or  variable,  as  desired. 

In  another  type  of  hydraulic  brake  the  throttling  bars  are  not 
used,  but  the  varying  apertures  are  obtained  by  cutting  grooves  of 
varying  width  or  depth  on  the  interior  of  the  cylinder. 

Figure  B  represents  another  method  of  varying  the  throttling 
grooves.  The  piston  (P)  is  held  rigidly  from  turning  and  the  valve 
(V)  is  rotated  by  means  of  a  spiral  groove  cut  in  the  cylinder  walls, 
in  which  lugs  on  the  valve  slide  during  recoil,  thus  rotating  the 
valve  and  varying  the  size  of  the  openings  through  the  valve  and 
piston.  This  method  is  used  to  a  considerable  extent  in  British  design. 
Figure  C  illustrates  a  method  of  central  throttling.  The  throttling 
rod  (R)  has  a  varying  diameter;  this  causes  the  amount  of  liquid, 
which  flows  between  it  and  the  hole  in  the  piston  (P),  to  vary  in  the 
manner  necessary  for  correct  throttling.  This  method  is  used  in 
some  French  designs. 

Counterrecoil,  or  the  return  of  the  gun  to  battery  after  completion 
of  the  recoil,  may  be  effected  by  springs  or  by  compressed  air  cylin- 
ders; the  latter,  in  connection  with 
the  recoil  brake,  forming  the  hydro- 
pneumatic  recoil  system. 

The   spring  method   of   effecting 
counterrecoil  may  be  used  in  all  gun 


FIG.  C. 


carriages  on  which  the  gun  recoils 
in  the  direction  of  its  axis.  These  include  pedestal  mounts,  barbette 
carriages,  turret  mounts,  and  all  wheeled  carriages  illustrated  by 
figures  F  and  G. 

In  the  smaller  carriages  of  these  types  the  springs,  initially  com- 
pressed to  the  desired  amount,  may  be  placed  between  the  piston 
and  the  rear  end  of  the  hydraulic  brake  cylinder,  which  is  lengthened 
for  that  purpose. 

In  some  carriages  of  this  type  the  hydraulic  brake  cylinder  moves 
with  the  gun  in  recoil,  the  piston  being  stationary.  In  such  construc- 
tions the  springs  are  usually  placed  around  the  hydraulic  brake 
cylinder,  and  are  compressed  between  a  flange  on  that  cylinder  in 
front  and  some  fixed  part  of  the  carriage  in  the  rear. 

In  larger  carriages  the  springs  are  arranged  in  separate  cylinders 
with  pistons  of  their  own,  two  to  four  of  these  spring  cylinders  being 
required,  see  figures  F  and  G. 

Figure  D  shows  a  spring  counterrecoil  mechanism  (spring  recu- 
perator) consisting  of  two  concentric  columns  of  springs. 

It  is  sometimes  necessary  to  use  telescopic  springs  as  shown  in 
figure  E,  when  a  single  column  would  not  permit  sufficient  recoil. 


41 


These  and  other  arrangements  of  counterrecoil  springs  will  be 
further  discussed  in  the  description  of  the  carriages  to  which  tney 
pertain. 

Compressed  gas  (either  air  or  nitrogen)  is  now  very  generally 
used  to  effect  counterrecoil.  Figures  H,  J,  K,  and  L  are  diagrams 
of  two  designs  of  hydropneumatic  recuperators. 


3OOOOOOO  OOOO  O 
>OOOOOOOOOO( 

1 

fl 

oooooooooo 

IOOOOOOOOOOC 

\ 

TDOO  oooo 

o  o  o  o  \_ 

"  oo  o  o  o  o 

o  o  o  o  oj_ 

V 

_>OOOOOOOOO  O(f 

Jo  o  o  o  o  o 

o  o  o  o  or 

I 

FIG.   D. 


FIG.  E. 


In  figures  H  and  J  the  recuperator  piston  (P)  forces  the  oil 
from  the  recuperator  cylinder  into  the  gas  reservoir  through  the 
port  (A)  when  the  gun  recoils.  Thus  the  gas  is  compressed  and 
the  necessary  energy  stored  up  to  return  the  gun  to  battery.  The 


SRRIMC3 


FIG.  F-  IM-BATTERX    OR  F1RIMC3 


EINP    OF"   F?EICOII— 


-  SF>RIMG    REICOli-. 


piston  may  be  attached  to  the  gun  and  move  with  it,  the  cylinder 
being  fastened  to  the  carriage,  or  the  cylinder  may  move  and  the 
piston  rod  be  fastened  to  the  carriage.  The  gas  is  given  sufficient 
initial  compression  to  hold  the  gun  in  battery  at  all  elevations. 


42 

The  type  of  recuperator  shown  in  figures  K  and  L  is  similar 
in  operation  to  that  of  figures  H  and  J,  but  in  the  latter  design 
the  oil  is  separated  from  the  gas  by  the  floating  piston  (FP). 


FIG.  H     IN-BA-rTETRV  OR    F"IRIINQ   f=>OSmorS 


FLOATING  PISTON 


FIG.    U       E/NP  OF"   RETCOIL- 


MVPRO-PrSETUMAT-IC  REICOIL-  SVSTEM 
WITH   F-t-O/VTlMCS    F^lS-rOTH 


RG.  K   IN-BATTETRV  OR 


p»osmofN 


AIR 


ruuio 


FIG. 


HVDRO- PNEUMATIC  RECOIL-    SVST'EIN'I   WITH  FT_UIP 

IM  PiREicrr  corsTAOT  WITH  THE:  >AIR 

The  hydropneumatic  recuperator  (or  counterrecoil  mechanism) 
may  be  separated  from  the  recoil  brake  or  the  two  may  be  combined 
in  one  unit. 


OIL 


.43 

The  principal  advantages  of  air  cylinders  over  spring  cylinders  for 
counterrecoil  are  the  reduction  in  weight  and  longer  life.  These 
advantages  are  especially  important  in  long-recoil  field  guns  or  how- 
itzers designed  to  be  fired  at  high  angles  of  elevation.  If  springs  are 
used  the  columns  are  long  and  heavy,  being  liable  to  breakage ;  while 
if  air  cylinders  are  used,  the  additional  pressure  needed  when  the 
guns  are  fired  at  high  angles  of  elevation  can  be  obtained  by  pumping 
more  air  into  the  cylinders. 

It  is  evident  that  the  energy,  in  whatever  way  obtained,  which 
effects  counterrecoil,  forms  a  part  of  the  total  energy  of  recoil.  The 
total  resistance  to  recoil  is  composed  of  the  resistance  offered  by  the 
brake,  the  resistance  due  to  friction,  the  resistance — either  plus  or 
minus — due  to  the  inclination  of  the  top  of  the  chassis  or  the  recoil 
slides,  and  the  resistance  due  to  the  counterrecoil  springs  or  air  cyl- 
inders, if  there  are  such  included 
in  the  recoil  system. 

The  counterrecoil  buffer  is  , 
provided  for  reducing  the  shock  / 
to  the  carriage  as  the  gun  is  re-  . 
turned  to  the  firing  position  by  FIG  M. 

the  counterrecoil  mechanism. 

In  figure  M  is  shown  a  type  of  buffer  which  is  used  to  some  extent. 
It  consists  of  a  rod  (B)  which  acts  inside  the  hollow  piston  rod  of  the 
recoil  cylinder.  A  method  similar  to  this  is  to  provide  a  separate 
cylinder  in  which  a  projection  of  the  recoil  piston  acts  during  the 
last  few  inches  of  recoil.  It  may  consist  of  a  dashpot  formed  at  the 
end  of  the  recoil  cylinder. 

The  use  of  the  counterrecoil  buffer  increases  the  stability  of  mobile 
artillery  carriages  by  preventing  their  forward  motion  as  the  gun 
runs  into  battery. 

Modern  field  guns  and  howitzers  are  mounted  so  as  to  have  a  long 
recoil  on  their  carriages  when  fired  horizontally.  When  certain  types 
of  these  guns  are  fired  at  high  angles  of  elevation  it  is  necessary  to 
reduce  the  length  of  recoil  to  prevent  the  breech  of  the  gun  from 
striking  the  ground.  This  reduction  is  effected  by  a  mechanism 
which  automatically  reduces  the  size  of  the  orifices  in  the  hydraulic 
brake  as  the  gun  is  elevated.  This  is  known  as  variable  recoil. 

If  no  counterrecoil  buffer  is  provided,  the  velocity  of  the  gun  when 
going  into  the  firing  position  under  the  action  of  the  counterrecoil 
springs  or  air  cylinders  is  at  a  maximum  just  as  it  reaches  that  posi- 
tion. If  an  arrangement  is  made  to  automatically  fire  the  gun  when 
it  has  this  maximum  forward  velocity,  it  is  evident  that  the  maximum 
velocity  of  free  recoil  will  be  reduced  by  the  amount  of  the  forward 
velocity,  and  hence  either  the  total  resistance  or  the  corresponding 
length  of  recoil,  or  both,  can  be  materially  reduced.  Systems  based 


44. 

upon  this  principle  have  been  used  abroad  for  small  guns,  such  as 
mountain  guns.  The  gun  is  caught  by  a  pawl  in  the  extreme  recoil 
position  and  is  loaded  in  that  position.  When  it  is  desired  to  fire, 
the  pawl  is  tripped,  the  gun  runs  forward  and  is  automatically  fired 
as  it  reaches  the  firing  position.  The  principal  objections  to  this 
system,  which  is  known  as  the  differential  recoil  system,  are  the 
unsteadiness  of  the  gun  at  the  moment  of  firing  and  the  possibility 
of  the  gun  being  turned  over  in  a  forward  direction  by  the  shock  of 
counterrecoil  if  a  misfire  should  occur. 

In  artillery  of  position,  the  gun  carriage  is  rigidly  bolted  to  a  fixed 
platform.  Its  mechanism  is  such  as  to  allow  the  gun  and  the  attached 
parts  to  recoil  on  firing.  The  hydraulic  brake  cylinder  and  its  piston 
are  attached,  respectively,  to  the  moving  and  fixed  parts  of  the  car- 
riage, or  vice  versa,  in  such  a  way  as  to  cause  the  piston  to  be  drawn 
through  the  cylinder  as  the  gun  recoils.  When  constant  total  resist- 
ance is  to  be  exerted  by  the  recoil  system,  which  is  always  the  case  in 
artillery  of  position,  either  the  total  resistance  or  the  length  of  recoil 
may  be  assumed,  and  the  other  determined.  While  the  assumption 
of  a  very  long  recoil  would  reduce  the  resistance  and  consequently 
the  strain  on  the  carriage  and  permit  its  parts  to  be  made  lighter,  the 
necessary  increase  in  the  length  of  the  recoil  slides  might  overbalance 
the  saving  in  weight. 

In  carriages,  such  as  mortar,  antiaircraft  gun,  and  the  latest  type 
barbette  carriages,  all  of  which  permit  the  firing  of  the  gun  at  high 
angles  of  elevation,  a  very  long  recoil  can  not  be  used,  because  the 
distance  from  the  breech  of  the  gun  to  the  supporting  platform  will 
not  permit  it.  Furthermore,  the  use  of  a  long  recoil  would  necessi- 
tate the  use  of  long  and  heavy  columns  of  counterrecoil  springs. 
Lack  of  space  also  prevents  the  use  of  a  long  recoil  on  turret  mounts. 

In  disappearing  carriages,  the  length  of  recoil  is  determined  more 
by  the  necessity  of  giving  the  gun  the  proper  movement  in  recoil  than 
by  limitation  of  the  strains  brought  upon  the  carriage. 

With  the  exception  of  the  disappearing  and  the  older  type  of 
barbette  carriages,  the  recoil  for  artillery  of  position  is  comparatively 
short. 

The  construction  of  all  modern  wheeled  carriages  is  such  as  to 
allow  the  gun  to  recoil  in  the  direction  of  its  axis.  The  resistance  to 
recoil  developed  by  the  recoil  system  pulls  forward  on  the  gun  and 
backward  on  the  carriage,  tending  to  move  the  latter  to  the  rear. 
Actual  motion  of  the  carriage  to  the  rear  is  prevented  by  a  spade 
sunk  in  the  ground  at  the  end  of  the  trail  of  the  carriage  and  so  con- 
structed as  to  present  a  broad  surface  to  the  ground  in  the  rear. 
Under  ordinary  conditions  the  ground  will  resist  a  pressure  of  40 
pounds  per  square  inch  of  spade  surface,  and  knowing  the  pressure 


45 

developed  by  the  pull  of  the  piston  rod,  which  is  the  only  force  acting 
on  the  carriage,  the  size  of  spade  can  be  determined. 

Another  effect  produced  by  the  resistance  to  recoil  is  a  tendency  to 
rotate  the  carriage  around  the  point  of  support  of  the  trail,  or  to 
cause  the  wheels  to  jump  from  the  ground.  Such  a  movement  is 
very  undesirable,  as  it  interferes  with  the  rapid  aiming  and  firing  of 
the  piece.  In  order  to  prevent  the  wheels  from  jumping  off  the 
ground  when  the  gun  is  fired,  it  is  necessary  that  the  product  of 
weight  of  the  carriage,  including  its  recoiling  parts  and  the  hori- 
zontal distance  of  the  vertical  through  their  center  of  gravity  from 
the  point  of  support  of  the  trail,  should  at  any  instant  be  greater 
than  the  product  of  the  force  opposing  recoil  and  the  perpendicular 
distance  from  its  line  of  action  to  the  point  of  support  of  the  trail. 
The  value  of  the  total  resistance  to  recoil,  that  will  be  just  insufficient 
to  cause  the  wheels  to  rise  from  the  ground  when  the  gun  is  in  the 
firing  position,  is  obtained  by  equating  moments  which  will  show 
that  a  value  of  this  resistance  small  enough  to  prevent  jump  of  the 
wheels  in  the  early  part  of  the  recoil  might  still  cause  jump  toward 
the  end  of  the  recoil,  as  the  moment  of  the  weight  of  the  recoiling 
parts  becomes  less. 

It  is  evident  that  safety  against  jump  can  be  maintained  and  the 
necessary  length  of  recoil  shortened  if,  instead  of  assuming  a  constant 
total  resistance,  we  assume  it  as  decreasing  to  such  an  extent  as  to 
remain  parallel  to  a  line  showing  the  maximum  permissible  values  of 
the  total  resistance  to  recoil  and  plotted  as  a  function  of  the  length  of 
recoil.  If  the  length  of  recoil  is  such  as  to  provide  a  factor  of  sta- 
bility when  the  gun  is  fired  at  horizontal,  the  carriage  will  be  stable 
at  all  higher  elevations,  as  the  lever  arm  of  the  total  resistance  of 
recoil  decreases  as  the  gun  is  elevated.  For  this  reason  reduction  of 
the  length  of  recoil  with  increase  of  elevation  in  howitzer  carriages 
does  not  impair  their  stability. 

The  initial  strength  of  the  counterrecoil  spring  columns  or  air 
cylinders  is  the  force  which  they  exert  against  the  gun  in  the  firing 
position.  This  force  must  be  great  enough  to  hold  the  gun  in  that 
position  at  the  highest  angle  of  elevation  at  which  it  is  to  be  fired,  as 
well  as  to  overcome  the  friction  on  the  recoil  sides  as  the  gun  runs 
forward  to  jthe  firing  position. 


AIMING  DEVICES  AND  SIGHTING  METHODS. 


Sights  will  be  discussed  briefly  in  this  handbook  merely  to  indi- 
cate their  application  to  field,  antiaircraft,  and  trench  materiel. 

In  order  that  a  projectile  from  any  gun  may  hit  the  target,  the 
gun  must  be  fired  at  a  certain  angle  of  elevation  depending  on  the 
range,  the  ballistic  characteristics  of  the  gun,  and  upon  the  relative 
difference  in  level  of  the  gun  and  target.  It  must  be  given  such  a 
direction  to  the  right  or  left  of  the  target  as  to  offset  the  deviation  of 
the  projectile  due  to  drift  and  wind.  The  sights  of  the  gun  provide 
means  of  determining  when  the  axis  of  the  gun  has  the  predetermined 
direction. 

When  the  piece  is  sighted,  both  in  elevation  and  direction  by 
sighting  directly  on  the  target,  the  method  is  known  as  direct  laying. 
This  is  precisely  the  same  operation  as  sighting  a  shoulder  rifle  or 
pistol.  The  line  of  sight  may  be  fixed  in  one  of  two  ways.  The 
first  method  is  to  use  plain  or  open  sights,  the  rear  one  of  which  has 
a  peep,  or  notch,  capable  of  adjustment  in  a  vertical  or  horizontal 
direction.  This  rear  sight  is  equipped  with  an  arc  reading  in  frac- 
tions of  the  range,  or  degrees  of  elevation,  by,  which  the  necessary 
elevation  can  be  set  off.  In  some  cases  the  rear  sight  is  designed  to 
automatically  correct  for  drift ;  if  not,  the  drift  must  be  set  off  on  a 
scale  provided  for  this  purpose  on  the  rear  sight.  It  is  always  well 
to  bear  in  mind  that  the  flight  of  the  projectile  follows  the  movement 
of  the  rear  sight,  going  higher  as  the  sight  is  raised,  and  to  the 
right  or  left  as  the  sight  is  moved  to  the  right  or  left. 

The  second  method  for  direct  laying  is  to  use  a  telescope  with 
cross  hairs  which  takes  the  place  of  the  open  sights,  although  the 
principle  of  operation  is  the  same. 

The  angle  of  elevation  of  a  gun  must  be  measured  in  the  vertical 
plane  through  the  axis  of  the  piece.  It  frequently  happens  that  a 
mobile  piece  must  be  fired  under  conditions  in  which  the  axis  about 
which  it  turns  in  elevation  (trunnion  axis)  is  not  level,  thereby 
throwing  the  sight  plane  out  of  the  vertical.  If  this  is  the  case, 
the  sight  arm  must  be  revolved  about  an  axis  parallel  to  the  axis 
^of  the  gun  until  the  sight  arm  is  vertical.  Most  wheeled  mounts 
have  such  a  provision  made  on  their  sights. 

Independent  Line  of  Sight. 

In  order  to  relieve  the  gun  pointer  from  the  necessity  of  set- 
ting the  elevation  on  the  sight  standard  and  elevating  the  piece, 
some  guns  are  provided  with  what  is  known  as  the  independent  line 

(46) 


47 

of  sight.     It  will  be  noted  that  the  actual  quadrant  elevation  of  the 
piece  consists  of  two  parts : 

(a)  The  elevation  necessary  to  reach  the  target  if  it  were  on  the 
same  level  as  the  gun. 

(Z>)  The  correction  to  this  elevation  required  by  the  difference  in 
level  of  the  gun  and  target  (angle  of  site). 

With  the  independent  line  of  sight  the  two  parts  of  the  quadrant 
elevation  are  applied  to  the  gun  independently.  An  intermediate 
rocker  and  two  elevating  systems,  A  and  B,  are  provided  as  shown 
in  Figure  N. 

The  sight  is  fixed  to  the  rocker,  and  for  direct  fire  the  gun  pointer 
manipulates  the  lower  elevation  system  A,  which  moves  the  rocker 
as  well  as  the  gun  in  elevation.  In  this  way  the  angle  of  site  is  auto- 
matically corrected,  when  the  line  of  sight  is  brought  upon  the  target. 

The  other  elevating  mechanism,  B,  is  between  the  rocker  and  the 
gun  and  is  manipulated  by  another  cannoneer,  who  elevates  the  gun 
until   the   proper   range   appears 
on  a  range  scale. 

The  change  in  range  does  not 
affect  the  setting  of  the  lower 
elevating  mechanism,  and  the  gun 
pointer  is  thus  free  to  devote  his 
whole  time  to  keeping  his  line  of 
sight  upon  the  target  and  is  not 
compelled  to  take  his  eye  from  the  telescope.  The  additional  mecha- 
nism necessary  for  this  system  is  more  than  offset  by  the  ease  of 
manipulation  secured. 

Various  modifications  of  this  general  method  of  securing  the  inde- 
pendent line  of  sight  are  in  use  and  will  be  discussed  with  the  guns 
to  which  they  pertain. 

The  gun  is  said  to  be  laid  indirectly  when  it  is  laid  by  means  other 
than  aiming  directly  through  the  sights  at  the  targets. 

The  fire  from  modern  fieldpieces  is  so  accurate  and  destructive  that 
it  is  always  necessary  to  establish  field  batteries  in  position  out  of 
the  view  of  the  enemy  for  the  sake  of  protection.  Indirect  sighting 
is  then  the  usual  method  of  sighting  such  guns. 

The  panoramic  sight  affords  the  means  of  aiming  the  gun  in  indi- 
rect laying  by  directing  the  line  of  sight  on  any  object  in  view  from 
the  gun;  at  the  same  time  it  affords  the  advantage  of  a  telescopic 
sight  in  direct  or  indirect  aiming. 

This  panoramic  sight  is  a  telescope  so  fitted  with  a  rotating  head, 
reflectors  and  prisms,  that  a  magnified  image  of  an  object  anywhere  in 
view  may  be  brought  to  the  eye  without  change  in  the  position  of 
the  observer's  eye. 
55160—21 4 


48 


The  panoramic  sight  is  often  mounted  in  connection  with  the  range- 
sighting  mechanism,  but  in  some  cases  in  order  to  divide  the  duties 
of  laying  for  direction  and  elevation,  the  panoramic  sight  is  mounted 
on  a  shank  on  the  left  side  of  the  cradle  and  used  in  laying  for  direc- 
tion, while  the  range  quadrant  for  laying  in  elevation  is  placed  on  the 
right  side  of  the  cradle  and  used  by  another  cannoneer. 

In  connection  with  the  range  quadrant  a  range  level  is  provided, 
which  is  a  special  form  of  clinometer.  It  is  used  in  setting  off  the 
angle  of  site,  thereby  correcting  for  difference  in  level  of  the  gun 
or  target.  The  range  quadrant  is  graduated  in  units  of  angular  eleva- 
tion or  in  fractions  of  the  range.  In  the  case  of  howitzers  the  different 
zones  of  fire  are  sometimes  shown. 

While  the  use  of  the  range  quadrant  separates  the  duties  of  the 
cannoneers  in  aiming,  it  does  not  comply  with  the  conditions  for 

the  independent  line  of  sight.  The  sight 
and  range  quadrant  being  attached  to  the 
cradle,  both  move  in  elevation  with  the 
gun.  The  independent  line  of  sight  per- 
mits of  the  gun  being  moved  and  set  in 
dS£iffi&lM  ^J^  j  elevation  without  any  change  in  position 

K  j  of  the  sight  used  for  direction  aiming. 

Leveling  plates  or  similar  surfaces  are 
provided  on  all  guns  and  howitzers  on 
which  a  gunner's  quadrant  (see  p.  49) 
can  be  used  in  obtaining  or  checking 
the  elevation. 

It  is  not  the  intention  to  go  into  detail 
in  this  handbook  regarding  the  fire- 
control  equipment  employed  for  direct- 
ing the  fire  of  antiaircraft  materiel,  but 
as  the  development  is  so  new,  and  they 
are  so  closely  involved  with  artillery 
during  operations,  it  is  quite  necessary 
to  devote  some  space  to  the  fire-control  equipment. 

Many  of  the  terms  and  instruments  used  in  connection  with  anti- 
aircraft artillery  are  similar  to  those  employed  with  field  artillery 
materiel,  but  the  methods  of  application  in  most  cases  differ. 

In  the  direct  fire  of  antiaircraft  artillery  the  following  angles 
resulting  in  the  laying  of  the  gun  to  the  predicted  future  position 
of  the  target  are  involved : 

1.  Present  azimuth  and  elevation.    These  are  obtained  by  direct 
sighting  upon  the  target. 

2.  Principal  lateral  and  vertical  deflections. 

3.  Secondary  lateral  and  vertical  deflections. 

4.  Superelevation. 


PANORAMIC  SIGHT, 
MODEL  OF  1917. 


49 


In  the  determination  of  the  principal  lateral  and  vertical  deflec- 
tions, two  methods  of  fire  control  have  been  established : 

1.  Linear  speed. 

2.  Angular  speed. 

Each  method  assumes  rectilinear  travel  of  the  target — i.  e.,  that 
the  pilot  of  the  aircraft  will  fly  a  straight  course  at  unchanging 
speed  and  constant  altitude  during  the  time  required  for  the  deter- 
mination of  the  fuse  range,  setting  of  the  fuse,  loading  and  firing 
the  gun,  and  for  the  projectile  to  reach  its  point  of  burst.  Each 
method  is  based  upon  sound  mathematical  reasoning  and  involves 
automatic  apparatus  of  rather  complex  but  easily  operated  mechan- 


GUNNER'S   QUADRANT,   MODEL   OF   1918. 

ical  and  electrical  design,  in  order  to  resolve  the  data  required  in 
the  laying  of  the  gun. 

In  the  first  method  the  quantities  required  in  the  resolution  of 
the  formulae  are : 

(a)  Presentation  (angle  of  approach)  ;  i.  e.,  the  horizontal  pro- 
jection of  the  angle  made  between  the  vertical  plane  of  sight  and 
the  axis  of  the  fuselage  of  the  airplane. 

(5)  Engine  speed  of  the  target. 

(c)  Altitude  of  the  target. 

(d)  Time  of  flight  of  the  projectile  to  the  future  position  of  the 
target. 


50 

The  resolution  of  the  formulae  deriving  the  lateral  and  vertical 
deflection  corrections  is  accomplished  upon  a  device  known  as 
"Antiaircraft  artillery  deflection  computer."  The  readings  ulti- 
mately obtained  from  this  instrument  are  given  in  mils.  They  are 
transmitted  telephonically  or  by  direct  announcement  to  the  gun 
layers  who  immediately  lay  the  gun  to  its  future  position,  while  the 
telescope  pointers  remain  sighted  upon  the  present  position  of  the 
target. 

The  great  advantage  of  this  method  lies  in  the  fact  that  the  pre- 
sentation and  engine  speed  can  be  estimated  with  reasonable  ac- 
curacy. The  altitude  of  the  airplane  is  determined  from  altimetry 
stations,  and  the  time  of  flight  is  known  when  fuse  range  has  been 
determined  from  a  telemeter. 

In  the  angular  speed  method  the  lateral  and  vertical  angular 
velocity  of  the  target  is  measured.  These  are  multiplied  by  the  total 
element  of  time  mentioned  in  the  aforesaid  and  gives  the  respective 
displacements.  The  fact  that  the  angular  velocity  of  an  airplane  in 
ordinary  flight  is  never  uniform  makes  this  method  more  difficult  of 
apprehension  but,  as  applied  in  our  instrument  design,  gives  results 
appreciably  better  than  the  linear  speed  method  and  is  consequently 
used  more  generally.  The  instruments  resolve  the  lateral  and  ver- 
tical deflection  corrections  in  mils  and  also  the  fuse,  range.  These 
are  telephoned  to  the  gun  layers  who  function  the  sighting  system 
mechanisms. 

The  element  fuse  range  is  required  for  two  main  purposes  in  anti- 
aircraft gunnery:  (a)  For  the  setting  of  the  fuse,  and  (5)  as  a  func- 
tion in  automatically  giving  superelevation  to  the  gun — i.  e.,  the 
angle  between  the  line  of  sight  to  the  predicted  future  position  of 
the  target  and  the  axis  of  the  bore  of  the  gun  when  ready  to  fire. 

Secondary  deflections  are  required  in  making  allowances  for  wind- 
age, ballistics,  drift,  etc.  These  are  set  by  giving  secondary  move- 
ment to  mechanisms  of  the  sighting  system. 

When  firing,  "  indirect "  or  at  night,  which  essentially  is  indirect 
fire,  three  elements  pertaining  to  the  predicted  future  position  of  the 
target  are  transmitted  from  this  apparatus  at  the  fire-control  station 
in  order  to  accomplish  the  laying  of  the  gun  and  setting  of  the  fuse : 

1.  Azimuth. 

2.  Quadrant  elevation. 

3.  Fuse  range. 

Secondary  deflections  involve,  in  addition  to  those  common  to 
direct  firing,  corrections  for  parallax  when  firing  "  indirect." 

At  night  the  alliance  of  listening  apparatus  and  searchlights  assist 
in  accomplishing  the  resolution  of  the  gun-laying  elements  at  the 
fire-control  station. 


51 

Altimetry,  which  is  a  basic  factor  in  the  computation  of  the  prin- 
cipal and  secondary  deflection  corrections,  is  obtained  in  one  of  two 
ways  : 

(a)  Monostatic. 

The  monastatic  or  one-station  instrument  is  an  optical  device  that 
determines  the  altitude  by  automatic  triangulation  through  the  coin- 
cidence of  light  rays  along  a  self-contained  base. 

(b)  Bistatic. 

This  is  a  system  in  which  two  stations  are  set  up  and  oriented 
along  a  base  line  of  known  length,  frequently  as  great  as  4,000 
yards.  The  height  or  vertical  distance  of  the  target  above  the  base 
line  is  then  determined  geometrically  by  projecting  its  altitude 
horizontally  into  the  vertical  plane  passing  through  this  base  line. 

When  altitude  has  been  determined,  the  observed  position  is 
resolved  into  the  future  position  by  automatic  devices. 

When  firing  against  airplanes  at  night,  searchlights  are  used  to 
illuminate  the  objective.  When  it  is  able  to  find  it  and  keep  it  in 
its  field,  firing  can  be  conducted  in  the  same  manner  as  in  day- 
time. Many  sound-detecting  instruments  have  been  made;  one  of 
the  recent  types  is  the  "  Paraboloid."  A  surface  in  the  shape  of  a 
paraboloid,  movable  in  azimuth  and  site,  focuses  the  sound  waves 
when  its  axis  is  placed  in  their  direction ;  they  swing  from  one  side  of 
the  focus  to  the  other  when  the  axis  of  the  instrument  is  turned. 
The  sound  is  received  by  trumpets  placed  on  either  side  of  the  focus 
and  joined  in  pairs  to  the  ears  of  two  observers  who  adjust  the 
instrument,  the  one  for  azimuth,  the  other  for  site. 

Briefly,  the  foregoing  describes  the  fundamentals  of  anti-aircraft 
artillery  fire-control  methods.  Being  the  most  precise  form  of 
gunnery,  anti-aircraft  artillery  involves  material  capable  of  the 
highest  degree  of  facility  and  accuracy  in  the  automatic  measure- 
ment of  deflections  and  the  maneuvering  of  its  gun-laying  mechan- 
isms in  order  that  effective  fire  may  be  conducted  against  a  target 
whose  movements  are  subject  to  such  large  displacements. 

(See  Ordnance  Document  No.  2037,  "  The  Manufacture  of  Optical 
Glass  and  of  Precision  Optics"} 

(See  War  Department  Document  No  1065,  "Handbook  on  Elemen- 
tary Optics  and  Applications  to  Fire-Control  Instruments") 


52 


ACCOMPANYING  VEHICLES. 


In  addition  to  the  piece  itself,  a  number  of  vehicles  are  necessary 
in  batteries,  sectors,  and  regimental  organizations  of  field  artillery 
for  maneuvering  and  serving  the  piece.  The  type  of  vehicles  vary 
with  the  different  guns  and  the  various  organizations.  Some  of  the 
more  common  vehicles  such  as  limbers,  caissons,  etc.,  are  described 
in  a  general  way  in  this  chapter,  while  their  special  features  are 
described  in  detail  with  the  materiel  with  which  they  are  issued. 
Other  special  vehicles  such  as  reels,  store  and  battery  wagons,  etc., 
are  also  described  with  the  materiel  to  which  they  pertain. 

The  caisson  is  essentially  a  conveyance  for  the  transportation  of 
ammunition  in  the  field.  It  generally  consists  of  a  chest  for  ammu- 
nition mounted  on  two  wheels  and  an  axle.  In  front  it  is  fitted  with  a 
short  pole  having  a  lunette  for  attachment  to  other  vehicles  and  in 
the  rear  with  a  pintle,  to  which  additional  vehicles  may  be  attached. 
Various  tools  are  usually  carried  on  the  caisson,  and  seats  are  pro- 
vided for  the  accommodation  of  the  personnel. 

The  limber  is  a  two-wheeled  vehicle  designed  primarily  to  increase 
the  mobility  and  facilitate  the  maneuvering  and  deployment  of  field 
artillery.  There  are  several  types  of  limbers  in  use,  the  principal 
ones  being  the  carriage  and  caisson  limbers. 

The  carriage  limber  is  attached  to  the  trail  of  the  piece  when 
traveling.  For  light  field  pieces,  a  chest  for  ammunition  is  pro- 
vided on  the  carriage  limber.  In  the  case  of  heavy  pieces,  the  chest 
is  dispensed  with  and  the  trail  of  the  piece  rests  on  the  top  section 
of  the  limber.  A  pole  is  provided  at  the  front  for  horse  or  motor 
traction,  and  the  rear  is  equipped  with  a  pintle  for  attachment  of 
the  carriage. 

The  caisson  limber  is  used  for  hauling  the  caisson  and  is  provided 
with  a  chest  for  carrying  ammunition. 

The  forge  and  store  limbers  are  designed  to  carry  supplies  and 
equipment,  the  forge  limber  carrying  the  tools  and  supplies  for  the 
farriers'  shop.  The  battery  wagon  and  the  store  wagon  are  two- 
wheeled  vehicles  equipped  with  chests  for  tools,  supplies,  and  spare 
parts. 

With  batteries  of  heavier  field  artillery,  some  of  the  vehicles  are 
dispensed  with,  especially  the  caissons,  battery  wagons,  forge,  and 
store  limbers,  the  ammunition  being  carried  in  motor  trucks,  in  which 
most  of  the  spare  parts  and  supplies  are  also  carried. 

(53) 


54 


Light  field  artillery  is  usually  drawn  by  horses  although  some  of 
these  batteries  are  now  motorized;  i.  e.,  hauled  by  either  caterpillar 
tractors  or  motor  trucks. 

In  addition  to  this,  provisions  are  made  for  a  limited  number  of 
trailers  for  use  in  carrying  light  guns  at  high  speed  behind  motor 
vehicles.  These  trailers  are  rubber  tired  and  for  high-speed  condi- 
tions ;  the  complete  gun,  with  carriage,  may  be  placed  on  this  trailer 
instead  of  being  transported  on  its  own  wheels. 

The  recent  struggle  in  Europe  brought  about  problems  which 
heretofore  have  never  existed  in  warfare;  and  to  meet  these, 
changes  have  been  made  in  every  arm  of  the  service,  the  greatest  and 


75-MILLIMETER  GUN  CARRIAGE  MOUNTED  ON  A  3-INCH  FiELD  GUN   TKAlLt-R. 

most  radical  change  being  the  motorization  of  artillery.  Mechanical 
transport  is  at  this  time  in  such  a  state  of  development  that  there 
is  no  need  of  dwelling  upon  its  numerous  advantages  over  animal 
draft. 

The  original  heavy  artillery  was  limited  to  guns  emplaced  in 
permanent  fortifications  and  guns  of  large  caliber  which  were  only 
moved  with  great  difficulty.  Light  horse-drawn  guns  and  howitzers 
comprised  the  mobile  artillery  for  use  in  the  field.  This  type  of 
artillery  was  ideal  for  quick  action  at  short  ranges. 

As  the  artillery  became  a  more  important  factor,  large  caliber  long- 
range  jruns  were  required.  The  movements  of  this  heavy  artillery  in 


55 

the  field  could  only  be  accomplished  in  one  way — by  motorizing  it. 
The  result  is  the  development  of  the  extremely  mobile  heavy  artillery. 

In  applying  motor  transportation  to  artillery,  types  of  motor 
vehicles  of  widely  varying  capacity  and  duty  are  required.  In  most 
cases  commercial  cars  and  trucks  are  used,  but  in  a  few  instances 
special  types  have  been  developed.  Motor  equipment  is  still  under- 
going changes,  all  tending  to  produce  apparatus  of  unfailing  depend- 
ability and  maximum  mobility  and  flexibility. 

Motor  apparatus  of  the  following  types  have  been  selected  as  the 
most  suitable  for  accomplishing  this  motorization :  First,  passenger 
cars,  both  light  and  heavy;  second,  motor  cycles  with  and  without 
side  cars;  third,  trucks;  fourth,  four-wheeled  trailers;  and  fifth, 
tractors  of  the  caterpillar  type. 

Passenger  cars  are  furnished  when  on.  the  march  and  when  occupy- 
ing a  position  on  the  lines.  Batteries  are  supplied  with  light  touring 
cars,  staff  cars,  and  motor  cycles  with  side  cars.  Battalion  and  regi- 
mental headquarters  are  also  supplied  with  light  touring  cars  and 
Westfield  military  bicycles.  A  motor  cycle  is  ideal  for  liaison  and 
work  of  similar  nature  requiring  rapid  transportation  for  one  or 
two  individuals.  The  motor  cycle  is  particularly  useful  when  trav- 
eling in  convoy  and  for  keeping  the  various  units  of  an  organization 
in  close  touch  with  each  other. 

Motor  trucks  are  necessary  for  carrying  supplies  and  ammunition 
from  the  depots  and  distributing  them  to  the  various  units.  A  great 
many  trucks  are  required  to  insure  unfailing  supplies  when  artillery 
is  in  action.  Because  of  the  uncertain  conditions  of  the  roads  back 
of  the  lines  sturdy  trucks  that  can.  pull  through  under  the  most 
unfavorable  conditions  are  employed. 

In  bringing  the  guns  into  position  it  is  often  necessary  to  cross 
ground  plowed  by  exploded  shells,  to  go  through  mud  and  deep  sand, 
and  to  ford  streams  which  can  not  be  negotiated  by  a  wheeled  type 
of  motor  vehicle,  thus  the  type  of  apparatus  adapted  for  this  purpose 
is  the  caterpillar  tractor. 

The  problem  of  the  care  and  maintenance  of  motor  equipment  in 
the  field  is  met  by  issuing  the  repair  and  artillery  supply  trucks  to 
each  battery  supply  and  headquarters  company  of  motorized  artillery. 

The  artillery  supply  truck  is  really  a  motorized  store  wagon  carry- 
ing spare  parts,  tools,  etc.,  for  the  particular  kind  of  unit  to  which 
it  is  assigned. 

The  artillery  repair  truck  consists  of  a  small  machine  shop  mounted 
on  wheels.  Its  equipment  is  complete,  including  a  lathe,  drill  press, 
air  hammer,  forge,  etc.  Electric  power  is  supplied  by  a  small  gen- 
erator driven  by  an  individual  gasoline  motor  mounted  on  the  truck. 
The  equipment  is  designed  to  make  all  repairs  in  the  field,  both  to 
artillery  materiel  and  motor  vehicles. 


56 

The  motor  equipment  makes  transportation  a  comparatively  easy 
matter,  permitting  it  to  be  moved  with  rapidity,  either  on  the  offensive 
or  defensive.  The  value  of  this  equipment  becomes  more  apparent 


as  the  nature  of  warfare  changes  from  that  of  position  to  that  of 
movement. 

Detailed  descriptions  of  the  above  motor  vehicles  are  given  in 
separate  handbooks  pertaining  to  motor  equipment  materiel. 

(See  War  Department  Document  No.  101$.) 


37-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1916. 


Experience  has  shown  that  the  infantry  can  not  carry  out  its  mis- 
sion by  its  rifles  and  machine  guns  except  at  prohibitive  loss  of  per- 
sonnel. The  individual  rifle  does  not  offer  the  necessary  volume  of 
fire,  while  the  rifle  grenade,  and  even  more  so  the  hand  grenade,  is 
a  close-combat  weapon.  Hence  the  taking  of  a  machine-gun  nest 
by  a  unit  (consisting  of  an  automatic  rifle  squad,  hand  bombers,  and 
rifle  grenadiers)  attacking  the  flanks  will  not  prove  very  successful, 
particularly  if  machine-gun  nests  are  echeloned  to  considerable  depth 
and  executing  cross  fire. 

Such  condition  calls  for  some  form  of  artillery,  effective  at  from 
400  to  1,500  meters,  against  both  personnel  and  materiel,  and  capable 


37-MILLIMETER    GUN    CARRIAGE    AND    AMMUNITION    CART,    LIMBERED. 

of  immediate  action.  The  field  artillery  is  not  available  because  of 
difficulty  of  communication  and  length  of  time  necessary  to  get  into 
action.  The  heavy  artillery  is  not  sufficiently  mobile.  Its  dispersion 
is  too  great  for  small,  definite  targets,  thereby  calling  for  vast  amount 
of  ammunition,  extremely  difficult  to  transport. 

The  necessity  of  providing  an  accompanying  gun  for  certain  units 
of  infantry  has  led  to  the  adoption  of  a  37-millimeter  gun  (devel- 
oped by  the  French  Army). 

The  37-millimeter  gun,  also  known  as  the  1-pounder  or  infantry 
accompanying  gun,  is  the  smallest  weapon  of  the  field-gun  type  in 
use  by  the  American  Army.  It  is  used  by  advancing  infantry  outfits, 
chiefly  for  destroying  concrete  machine-gun  emplacements,  outposts, 
and  other  points  of  resistance.  Recent  developments  and  modifica- 
tions of  this  weapon  have  found  wide  application  for  its  use  and,  due 
to  its  extreme  portability,  this  gun  is  adaptable  for  tanks,  tractors, 
and  aircraft. 

(57) 


58 

As  this  gun  is  intended  to  follow  infantry  over  any  kind  of  ground 
its  construction  is  designed  to  give  great  mobility.  The  personnel 
is  organized  for  rapid  fire;  the  possible  rapidity  of  fire  is  35  shots 
per  minute. 

Each  gun  unit  is  composed  essentially  of  two  elements : 

(1)  The  gun  on  a  tripod  mount,  capable  of  being  set  on  wheels. 

(2)  A  light  wagon  serving  as  a  limber  and  carrying  ammunition, 
spare  parts,  and  accessories. 

The  gun  and  limber  when  joined  are  normally  hauled  by  one 
horse  or  mule,  but  near  the  enemy  they  are  separated  and  moved 
by  man. 

In  action  the  gun  is  operated  by  two  men,  one  keeping  it  on  the 
aiming  point  and  the  other  loading  and  firing.  The  gun  must  be 
cocked  by  hand  in  order  to  load  for  the  first  round,  but  thereafter 
the  counterrecoil  of  the  barrel  cocks  the  piece,  and  it  is  only  neces- 
sary to  open  the  breech  mechanism,  which  ejects  the  case,  insert  a 
new  cartridge,  close  the  breech,  and  fire. 

When  used  as  a  tripod  mount,  it  is  separated  into  portable  groups 
for  transportation  and  each  unit  is  carried  by  two  men.  One  group, 
weighing  104  pounds,  consists  of  the  gun  and  cradle  and  the  other  of 
the  trails,  weighing  84  pounds.  With  the  combination  tripod  mount,, 
the  gun  is  transported  on  a  wheeled  carriage  which  is  limbered  to  a 
two- wheeled  ammunition  cart,  drawn  by  one  mule  or  horse. 

Wcigths,  dimensions,  and  ballistics. 

Weight  of  gun  and  recoil  mechanism  (with  flash  hider  and  sight)  -pounds 104 

Weight  and  recoil  of  group do 34 

Weight   of  barrel   group __do__  38 

Weight  of  breech  group — do 18 

Weight  of  flash  hider do 2.  5 

Length   of   gun calibers 20 

Range   (H.  E.  Shell  Mark  II) meters—  3,650 

Muzzle  velocity feet  per  second 1.204 

Weight  of  projectile pounds—  1.234 

Length   of   recoil inches—     7-10 

Maximum  angle  of  elevation degrees 21 

Maximum   angle   of  depression do 14 

Amount   of  traverse   to   right '__ do 22 

Amount  of  traverse  to  left do 16 

Weight  of  axle,  complete pounds 36.  25 

Weight  of  wheels,  each do 68 

Weight  of  trails  (including  pintle  and  float) do 84 

Diameter  of  wheels inches—  37.75 

Width  of  track —do 33 

Weight  of  gun  and  carriage,  complete pounds—      360 

Over-all   length  of  vehicle inches—        75 

Over-all  height  of  vehicle do 37.  75 

Over-all  width  of  vehicle..  — do —  57 


59 


60 

The  gun  is  composed  mainly  of  a  steel  alloy  barrel.  A  front  clip 
of  bronze  and  an  aluminum  jacket  serve  as  supports  and  guides  for 
the  whole  barrel.  The  breech  housing  is  screwed  to  the  rear  end  of 
the  barrel  and  forms  a  receptacle  for  the  breechblock. 

The  breechblock  is  of  the  Nordenfeld  type  and  with  the  exception 
of  size  is  practically  the  same  as  that  used  on  the  French  75  milli- 
meter field  gun.  It  screws  into  the  breech  housing  and  is  opened 
and  closed  by  being  rotated  156  degrees  about  its  axis,  which  move-, 
ment  is  limited  in  each  direction  by  a  stop.  The  breechblock  is 
cylindrical  in  form,  rotates  in  a  threaded  seat  and  is  operated  by  a 
handle  which  when  moved  to  the  left  causes  the  eccentric  hole  in 
the  block  to  register  with  the  bore  and  also  operates  the  extractor 
thus  ejecting  the  empty  cartridge  case.  Pulling  the  lever  to  the 
right  rotates  the  block  so  that  the  port  in  the  block  is  drawn  away 
from  the  bore  and  a  solid  surface  containing  the  firing  pin  backs  up 
to  the  base  of  the  cartridge. 

The  action  of  the  powder  gases  on  the  breechblock  at  the  moment 
of  discharge  produces  the  recoil  of  the  united  barrel  and  breechblock. 


TRIPOD   MOUNT   IN*   FIRING   POSITION. 


The  purpose  of  the  recoil  mechanism  is  to  control  and  limit  the  recoil 
and  to  return  the  barrel  to  the  firing  position,. at  the  same  time  pre- 
venting a  sudden  return  which  might  disturb  the  aim  of  the  gun. 

The  recoil  cylinder  consists  of  a  cylinder  containing  a  piston, 
piston  valve,  counterrecoil  spring  in  three  sections,  and  counterrecoil 
buffer.  The  piston  rod,  which  is  hollow  and  open  at  the  piston  end, 
is  pierced  with  holes  for  the  passage  of  oil  both  during  recoil  and 
counterrecoil.  The  piston  is  fitted  with  four  holes  for  the  passage 
of  oil  during  recoil.  This  oil  is  allowed  to  pass  through  two  parts 
of  the  piston ;  first,  through  the  hollow  portion  of  the  piston  rod,  and 
second,  through  the  holes  in  the  piston  head.  The  oil  passages  in 
the  piston  head  are  closed  by  the  piston  valve.  The  valve  is  held 
against  the  front  face  of  the  piston  by  a  spring,  closing  the  oil  holes 
in  the  head  during  the  counterrecoil  stroke,  thus  slowing  up  the  for- 
ward motion  of  the  gun.  The  counterrecoil  buffer  is  screwed  into 
the  front  cylinder  cap  and  eases  the  movement  of  the  gun  into 
battery,  thus  preventing  excessive  shock.  The  capacity  of  recoil 
cylinder  is  2.75  pints  and  the  extreme  travel  of  the  piston  is  11  inches. 


61 

• 

The  mount  may  be  used  either  in  the  form  of  a  tripod  or  with  the 
axle  and  wheels  attached.  In  the  former  case  a  front  leg  having  a 
float  adjustable  to  two  heights  at  its  lower  end  is  used  to  support  the 
front  end  of  the  mount,  and  the  spread  trails  in  rear  equipped  with 
spades  form  the  other  points  of  support.  In  the  case  of  the  wheels 
being  used,  the  front  leg  is  swung  up  and  secured,  and  both  trails 
are  spread  out  to  support  the  rear. 

The  pintle,  or  gun  mount,  is  in  the  form  of  a  yoke,  the  upper  end 
being  fitted  to  receive  the  cradle  trunnions.  Each  trail  head  is 
equipped  with  lugs  which  pivot  on  bearing  surfaces  in  the  lower  end 
of  the  pintle.  The  trails,  when  spread,  are  kept  in  position  by  a 
removable  transom,  which  also  serves  as  a  seat  for  the  gunner. 

A  Y-shaped  frame,  pivoted  and  secured  to  the  pintle  at  its  upper 
and  lower  ends,  extends  to  the  rear  in  the  form  of  a  fork  and  engages 
the  nut  housing  on  the  traversing  screw.  The  nut  is  turned  in  its 
housing  by  a  small  handwheel  attached  thereto,  which  causes  the 


GUN  DISASSEMBLED  ON  THE  MARCH   (WHEELS  AND  AXLES  LEFT  IN  THE  REAR). 

nut  and  housing  to  move  along  the  screw,  thereby  traversing  the 
gun.  The  screw  is  pivoted  in  the  left  trail  and  moves  in  and  out 
through  a  bushing  pivoted  in  the  right  trail  when  the  trails  are  being 
spread  or  closed.  When  the  trails  are  to  be  closed,  the  gun  is  trav- 
ersed to  the  extreme  right. 

The  elevating  mechanism  is  located  on  the  frame  in  front  of  the 
traversing  mechanism.  A  screw  fitting  into  a  nut  pivoted  in  the 
frame  is  raised  and  lowered  by  a  handwheel  attached  to  its  upper  end. 
Above  the  elevating  handwheel  is  a  hook  engaging  a  pin  fitted  to 
the  underside  of  the  cradle,  thus  the  rear  end  of  gun  is  secured  to 
the  trail  and  the  elevation  accomplished  when  the  cradle  is  mounted 
in  the  trunnion  bearings. 

A  conical  sheet  metal  flash  hider  is  secured  to  the  muzzle  of  the 
gun.  Some  of  these  carriages  are  equipped  with  an  armor  plate 
shield,  suitably  reinforced  by  stiffeners.  The  shield  consists  of  three 
plates  hinged  together,  and  is  mainly  employed  to  protect  the  gun- 
ners from  shrapnel  and  flying  fragments. 


62 


The  gun  is  provided  with  a  telescopic  sight  for  use  in  direct  fire 
and  a  quadrant  sight  for  indirect  or  masked  fire,  either  of  which  is 
mounted  on  the  left  side  of  the  gun  and  in  a  bracket  which  is  part  of 
the  striker  rod  housing. 

The  wheels  are  37.75  inche%  in  diameter  and  have  steel  tires  1.875 
inches  in  width. 

The  ammunition  is  of  the  fixed  type  having  a  steel  projectile  weigh- 
ing 1.097  pounds  containing  high  explosive,  and  detonated  by  a 
base  percussion  fuse.  A  complete  round  of  ammunition  weighs  1.47 
pounds  and  is  composed  of  projectile,  brass  case,  primer,  and  powder 
charge. 


GUN  AND  PERSONNEL  ON  THE  MARCH   (AMMUNITION  CART   LEFT  IN  THE  REAR). 

AMMUNITION  CART  FOR  THE  37-MILLIMETER  GUN. 

The  37-millimeter  gun  limber  (of  the  machine  gun  ammunition 
wagon  type)  is  essentially  a  frame  resting  on  two  shafts  having  a 
movable  bolt  and  rear  fittings  by  means  of  which  it  can  be  joined 
to  the  gun  mount. 

The  limber  carries  14  ammunition  boxes,  each  containing  16  car- 
tridges packed  in  a  fiber  packing  strip.  There  are  also  provided  2 
wooden  boxes  for  carrying  spare  parts,  tools,  accessories,  etc. 


2.95-INCH   VICKERS-MAXIM   MOUNTAIN   GUN  MATfiRIEL. 


WITH  PACK  OUTFIT. 

The  2.95-inch  Vickers-Maxim  mountain  gun  materiel  is  of  Vickers 
design  and  American  and  British  manufacture.  This  materiel  is 
intended  for  transportation  by  pack  animals;  for  this  reason  it  is  a 
light,  compact  weapon,  separating  very  quickly  and  easily  into  four 
loads  for  packing. 

The  cradle  is  carried  as  one  load,  the  wheels  and  axes  as  another, 
the  trail  another,  and  the  gun  as  the  fourth.  Four  other  pack  animals 
carry  the  pioneer  tools,  blacksmith's  tools,  supply  chest,  and  signal 
tools,  respectively.  Additional  pack  animals  are  employed  to  carry 
the  ammunition  for  the  battery.  Suitable  pack  frames  with  all  the 
necessary  attachments  are  provided  for  holding  the  load  compactly 
and  in  proper  place  on  the  animal. 

Weights,  dimensions,  and  ballistics. 

Caliber mches__  2.953 

Length  of  gun '. do 35.  85 

Weight  of  gun,  including  breech  mechanism pounds 2"-6 

Rifling  uniform,  1  turn  in  25  calibers,  right-hand  twist. 

Weight  of  projectile do 12J 

Weight  of  power  charge ounces 8 

Muzzle  velocity I: feet  per  second —      920 

Maximum   range , yards 4,  825 

Length  of  recoil  of  gun inches 14 

Height  of  axis  of  gun  above  ground do 26 

Maximum  angle  of  elevation degrees 27 

Maximum  angle  of  depression do 10 

Amount  of  traverse  of  gun  on  carriage do 0 

Diameter  of  wheels inches 36 

Width  of  track do 32 

Weight  of  carriage  only pounds 595 

Weight  of  gun  and  carriage do 830 

The  gun  barrel  is  a  one-piece  steel  forging,  cylindrical  in  form. 
On  either  side  of  the  breech  end  two  lugs  are  provided  to  which  the 
piston  rods  are  secured  when  the  gun  is  mounted  in  the  cradle.  For- 
ward of  these  lugs  is  a  finished  surface  of  uniform  diameter  which 
constitutes  a  bearing  for  the  gun.  This  surface  is  supplemented  at 
the  forward  end  of  the  gun  by  two  collars  of  equal  diameter,  thereby 
55160—21 5  (63) 


64 

insuring  a  firm  bearing  for  the  gun  in  the  cradle,  either  in  recoil  or 
in  battery.  At  the  bottom  of  the  barrel  is  a  guide  which  slides  in  a 
corresponding  groove  in  the  cradle,  thus  keeping  the  gun  in  proper 
position  and  preventing  it  from  turning  when  in  action. 


The  breech  mechanism  is  of  the  interrupted-screw  type.  A  handle 
which  operates  from  left  to  right  turns  and  swings  the  block  clear  with 
one  motion.  The  firing  pin  is  operated  by  means  of  a  trigger  which 
is  pulled  by  the  firing  lanyard.  A  safety  device  is  incorporated  to 
prevent  firing  when  the  breech  is  not  closed.  The  breech  is  equipped 
with  an  extractor  which  ejects  the  empty  cartridge  case  after  firing. 


65 

The  recoil  mecJianism  is  of  the  hydrospring  type.  It  is  known  as 
the  short-recoil  type  in  which  the  gun  is  permitted  a  length  of  recoil 
upon  the  carriage,  sufficient  to  diminish  the  movement  of  the  carriage 
on  the  ground  but  not  sufficient  to  render  the  carriage  stable.  To 


u 

3 

Z 
3 
0 


LJ 

J 

I 

J 
U 
U 
I 


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retard  the  movement  of  the  carriage  on  the  ground  the  wheels  are 
locked  by  means  of  "  brake  ropes,"  which  lock  the  wheels  to  the  traiL 
Two  buffer  cylinders,  one  on  each  side  of  the  gun,  are  bored  in  the 
cradle  casting.  They  contain  both  the  recoil  and  counterrecoil 
mechanism.  The  cylinders  are  connected  at  the  rear  by  a  by-pass 
which  keeps  the  oil  pressure  equal  in  the  two  cylinders.  Throttling 


66 

1  is  obtained  by  grooves  of  varying  width  in  the  cylinder  liners.  The 
piston  rods  are  attached  to  the  gun  by  means  of  interrupted  screws, 
which  permit  quick  removal  for  transportation. 

The  counterrecoil  mechanism  consists  merely  of  springs  wound 
around  the  piston  rods,  which  are  compressed  on  firing  and  which 
return  the  gun  into  battery. 


REAR   VIEW   OF   CARRIAGE. 

The  cradle  is  a  bronze  casting  comprising  three  parallel  cylinders. 
The  central  cylinder  supports  the  gun  from  the  breech  to  within  a  few 
inches  of  the  muzzle.  The  other  two,  as  before  stated,  accommodate 
the  recoil  mechanism.  In  place  of  trunnions  there  are  two  lugs 
underneath  the  cradle  through  which  passes  the  cradle  axis  bolt,  by 
means  of  which  the  cradle  is  secured  to  the  trail.  This  bolt  is  pro- 
vided with  a  handle  and  suitable  catch  for  quick  removal  when 


67 


disassembling  for  packing.  The  cradle  also  carries  the  sight  bracket 
and  has  a  plane  surface  on  top,  on  which  the  gunner's  quadrant  may 
be  used. 

The  elevating  gear  consists  of  a  quadrant  with  a   worm  wheel 
segment  thereon  operated  through  suitable  gearing  by  a  handwheel 


DETAILED   VIEW   OF   GUN. 


on  the  left  side  of  the  trail.  A  bolt  for  quick  release  of  the  elevating 
mechanism  from  the  cradle  is  provided.  Elevations  from  10  degrees 
depression  to  27  degrees  elevation  may  be  obtained. 


SIDE   VIEW  OF   CARRIAGE   IN   BATTERY. 

No  traversing  mechanism  is  provided,  and  traverse  must  there- 
fore be  obtained  by  swinging  the  trail. 

The  trail  consists  of  two  steel  side  plates  connected  by  crosspieces 
and  transoms.  The  front  crosspiece  contains  bearings  for  the  axle, 
cradle  axis  bolt,  and  elevating  gear.  A  shoe  at  the  rear  end  of  the 


68 


trail  is  fitted  with  a  "scraper,"  which  in  reality  is  a  short  spade.  It 
is  also  provided  with  a  socket  for  the  handspike. 

The  axle  is  a  solid  cylindrical  bar  with  flats  cut  on  two  sides  for 
securing  it  in  the  front  crosspiece  of  the  trail.  It  is  quickly  removable 
for  packing  and  is  carried  on  the  same  pack  animal  as  the  wheels. 
The  wheels  are  36  inches  in  diameter  and  are  steel  tired. 

Sighting  is  accomplished  by  means  of  the  sight,  model  of  1912, 
combined  with  either  an  open  sight  or  the  panoramic  sight 

The  sight  shank  is  a  steel  arc  which  can  be  moved  up  and  down  in 
elevation  by  means  of  a  scroll  gear.  A  range  strip  on  the  rear  face  of 
the  arc  is  graduated  in  50-yard  divisions  up  to  the  maximum  range 
of  the  piece. 

Combined  with  the  sight  is  a  graduated  level  which  serves  the  same 
purpose  as  the  range  quadrant  used  on  the  3-inch  equipment  and  other 
materiel  of  that  type.  By  this  means  the  piece  is  laid  for  elevation. 

The  sight  is  mounted  on  the  left  side  of  the  cradle.  By  having  the 
quadrant  level  and  sight  thus  combined  one  man  can  lay  for  both 
elevation  and  direction. 

The  ammunition  used  is  of  the  fixed  type,  consisting  of  steel 
high-explosive  and  shrapnel  shells,  each  weighing  12J  pounds.  Each 
animal  carries  two  chests  containing  five  rounds  each. 

COMPARATIVE  TABLE  OF  LIGHT   FIELD   GUNS  USED  IN  THE  WORLD   WAR. 


Austria, 
1905. 

France, 
1897. 

Ger- 
many, 
1896  n/a 

Great 
Britain, 
1917. 

Italy, 
1912. 

Ru^ia. 
1903. 

United 
States, 
1902. 

United 
States, 
1916. 

Caliber,  inches  

3.01 

2.95 

3.03 

3.3 

2.95 

3. 

3. 

2.95 

Weight  of  shrapnel,  pounds  

14.72 

16.00 

15.00 

16.00 

143 

14.41 

15.00 

16.00 

1,640 

1,955 

1,760 

1,900 

1,510 

1,930 

1,700 

1,900 

Muzzle  energy,  foot-tons     

275 

335 

242 

340 

224 

373 

300 

311 

Weight  of  gun  

700 

1,000 

766 

995 

690 

785 

835 

749 

Weight  of  gun  and  carriage  .        ... 

2,000 

2,650 

1,860 

2,890 

2,260 

2,075 

2,520 

3,045 

Weight  of  gun  caisson  and  limber  
Maximum  elevation  

3,750 
18 

4,150 
19 

4,200 
16 

4,420 
16 

3,350 
65 

3,850 

4,490 
15 

4,556 
53 

Total  traverse,  degrees           

8 

6 

8 

8 

52 

5i 

8 

45 

Length  of  recoil,  inches  .  .  .  .  '.  

51.5 

45 

44 

28-49 

18-53 

42.5 

45 

18-46 

Diameter  of  wheels  

4'3" 

4'4J* 

4'5J" 

4'8" 

4'3}" 

4'4" 

4'S" 

V8" 

Independent  line  of  sight  

No. 

Yes 

No. 

Yes. 

Yes. 

No. 

No. 

Yes. 

Sight,  goniometric,  telescopic,  pano- 
ramic, ordinary                

P. 

G. 

T.  G. 

O.  P. 

T.  P. 

O.  P. 

O.  P. 

0.  P. 

Breech  block,  wedge  swinging,  eccen- 
tric screw                           

W. 

E.  S. 

W. 

S. 

W. 

S.  B. 

S.  B. 

W. 

Traverse,  axle  or  pintle  

P. 

A. 

P. 

A. 

P. 

A. 

A. 

P. 

Recuperation,  spring  or  hydropneu- 
matic  

8. 

H. 

S. 

H. 

H. 

S. 

S. 

S. 

Length  of  gun,  calibers 

30 

34.5 

27.0 

28.4 

30 

34 

29.2 

28.4 

Width  of  track,  inches  

60 

60 

60 

60 

58 

60 

60 

60 

Range,  maximum  

6,400 

9,350 

7,600 

8,100 

8,850 

7,800 

8,500 

12,500 

75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1916. 


The  United  States  75 -millimeter  field  gun,  model  1916,  is  of  the 
split  trail  type,  permitting  greater  traverse  and  greater  elevation 
than  either  the  French  or  British  models  of  this  caliber,  equipped 
with  the  single  trail. 


FRONT   VIEW   OF   CARRIAGE. 

The  75-millimeter  field  gun  constitutes  the  light  field  artillery  of 
the  Army.  The  caliber  of  the  piece  is  about  as  large  as  ready  horse- 
drawn  mobility  will  permit.  The  caliber  is  equivalent  to  2.95  inches, 
and  was  adopted  by  the  French  and  by  the  Italians,  while  the  United 
States  had  adopted  the  3-inch  caliber,  and  Great  Britain  a  caliber 
of  3.3  inches  which  is  the  caliber  of  their  18-pounder.  The  German 
caliber  was  77  millimeters,  equivalent  to  3.03  inches.  The  points  of 
excellence  obtained  from  these  field  pieces  are :  good  range,  rapidity 
of  fire,  ease  of  transportation,  and  reliable  functioning. 

(69) 


70 


71 

The  American  model  1916  split-trail  carriage  permits  great  eleva- 
tion, within  the  mechanism  of  the  carriage,  and  likewise  a  wide 
traverse  without  changing  the  position  of  the  trail.  The  recoil  mech- 
anism was  adapted  to  the  higher  permissible  elevation  of  the  gun. 
and  equipped  with  a  variable  recoil,  automatically  adjustable  for 
different  elevation.  The  ability  to  outrange  the  enemy  is  constantly 
being  sought,  and  high  elevation  and  improvements  of  the  projectile 
are  the  means  through  which  it  is  hoped  to  obtain  the  increased  range 
desired.  Likewise,  a  wide  horizontal  arc  of  fire,  without  resetting  of 
the  trail  and  consequent  resetting  of  the  sighting  devices,  is  a  great 
convenience  and  saver  of  time. 


REAR   VIEW   OF   CARRIA( 


As  the  range  depends  not  only  on  the  power  of  the  gun  and  the 
design  of  the  ammunition,  but  also  on  the  elevation  provided  for,  and 
as  the  horizontal  arc  which  can  be  covered  by  a  gun  with  a  single 
setting  of  its  trail  is  governed  by  the  permissible  traverse,  attention 
is  invited  to  the  mechanical  features  covering  the  vertical  and  hori- 
zontal limits  of  the  gun  laying,  as  well  as  to  the  functioning  of  the 
piece.  Of  the  above  types,  the  French  model  has  been  credited 
with  functioning  most  perfectly,  but  it  lacks  provision  for  high  eleva- 
tion and  wide  traverse  of  the  gun.  Due  to  its  greater  elevation,  the 
American  piece  outranges  the  French,  although  the  French  gun  has 
a  greater  muzzle  velocity.  (See  page  89.) 

Compared  with  the  British  model  1917,  the  American  3-inch 
model  1902  carriage  permits  of  a  maximum  angle  of  elevation  of 
15°,  depression  of  5°,  and  traverse  of  142  mils,  while  the  British  model 
permitted  16°  elevation,  5°  depression,  and  142  mils  traverse.  The 
French  model  1897  carriage  permits  a  maximum  angle  of  elevation 
of  19°,  depression  10°,  and  traverse  106  mils.  The  American  model 


72 


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73 

1916  carriage  allows  a  total  vertical  movement  of  from  53°  elevation 
to  7°  depression  and  a  traverse  of  800  mils  (an  artillery  mil  equals 
the  angle  subtended  by  T*T  of  the  circumference  of  a  circle).  The 
American  model  1902  carriages  are  arranged  with  a  hydro-spring 
recoil  mechanism,  and  so  is  the  British  model  1917,  and  the  Ameri- 
can model  1916.  The  French  model  1897  carriage  is  equipped  with  a 
hydropneumatic  recoil  mechanism. 

The  weight  of  the  piece,  including  the  carriage  and  limber,  is 
about  4,500  pounds,  which  is  slightly  above  the  horse-drawn  draft 
limitation  over  rough  ground. 

The  introduction  of  motor  tractors  may  alter  the  draft  problem, 
but  there  still  remains  the  question  of  facility  in  handling  the  piece 


LEFT   SIDE   VIEW   OF   CARRIAGE. 


by  man  power  after  battery  position  has  been  reached.  As  one  phase 
of  this,  it  may  be  mentioned  that  the  weight  at  the  end  of  a  75- 
millimeter  gun-carriage  trail  is  only  approximately  100  pounds. 
The  trail  can  be  readily  unlimbered  and  spaded  into  position  or  its 
position  changed  by  man  power  within  a  few  moments,  while  to 
unlimber  and  spade  into  position,  or  to  change  position  of  the  trail 
of  a  155-millimeter  gun  requires  the  use  of  jacks  and  a  considerable 
expenditure  of  time. 

Rapidity  in  moving  a  fieldpiece  from  point  to  point,  where  railroad 
transportation  is  not  available,  is  not  entirely  a  matter  of  the  speed 
of  the  tractor,  for  likelihood  of  damage  to  the  materiel  when  trans- 
ported at  high  speed  on  its  own  wheels  must  also  be  considered.  The 
dimensions  and  weight  of  the  75-millimeter  piece  permit  of  its  being 
placed  on  a  rubber-tired  trailer  and  transported  at  high  speed  behind 
a  motor  vehicle. 

The  mobility  of  artillery  is  of  utmost  importance,  and  the  75- 
millimeter  field  gun  has  therefore  become  a  gun  of  first  rank,  as  it 
constitutes  the  light  artillery  of  the  military  powers.  This  weapon 


74 

is  accurate,  has  a  range  up  to  7  miles,  is  suitable  for  the  projection 
of  high  explosive,  shrapnel,  and  gas  projectiles,  destruction  of  per- 
sonnel, of  wire  entanglements,  and  of  fair-sized  obstacles,  and  to  some 
extent  the  destruction  or  protection  of  lines  of  communication. 

Weights,  dimenaions,  and  ballistics. 

Weight  of  gun  and  breech  mechanism pounds  749 

Length  of  gun inches__      90.9 

Caliber millimeters..          ~~> 

Length  of  bore inches. _          84 

Length,    calibers fS&  1 

Rifling,  right-hand  twist ;  increases  from  one  turn  in  119  calibers  at  the 
beginning  of  rifling  to  one  turn  in  25.4  calibers  at  a  point  9.72  inches 
from  muzzle.  Uniform  from  this  point  to  end  of  muzzle. 

Number  of  grooves 24 

Muzzle  velocity : 

Shrapnel  Mark  I  (21-second  combination  fuze) feet  per  second __     1,693 

.    Shell  Mark  IV  (armed  with  Mark  V  fuze) __<lo__        1,900 

Shell  Mark  I  (armed  with  Mark  V  fuze) ,_<!<>_  1,  74'J 

Maximum  range : 

Shrapnel  (Mark  I  shell) —yards.*     9,653 

Shell   (Mark  IV) _ —do 12,360 

Shell    (Mark  I) _-_ do__        8,780 

Range  at  10°  elevation do__     '    6,170 

Range  at  20°  elevation do..        9, 185 

Range  at  30°  elevation do 11,  385 

Weight  of  carriage,  complete  (without  gun) pounds 2,280 

Weight  of  gun  and  carriage,  fully  equipped do 3,045 

Diameter  of  wheels inches 56 

Width  of  track do—  60 

Length  of  recoil  of  gun  on  carriage  (variable) do 18-46 

Height  of  axis  of  gun  above  ground do 41.625 

Weight  at  lunette,  carriage  limbered pounds 140 

Height  of  center  line  of  peep  sight  above  ground inches 56.875 

Height  of  center  line  of  panoramic  sight  above  ground do 52 

Amount  of  elevation  with  elevating  handwheel degrees 42 

Over-all  width  of  trails,  spread inches..        130 

Over-all  length,  muzzle  of  gun  to  end  of  lunette do 173 

Length,  center  line  of  wheel  to  center  of  lunette do 118.  28 

Maximum  angle  of  elevation degrees 53 

Maximum  angle  of  depression do 7 

Maximum  transverse,  each  side  of  center mils 400 

Maximum  angle  of  elevation  with  angle  of  site  handwheel degrees 11 

Maximum  angle  of  depression  with  angle  of  site  handwheel do 7 


75-MILLIMETER  GUN  AND  CARRIAGE,  MODEL  OF  1916. 


The  gun  is  of  the  built-up  construction  and  consists  of  a  tube, 
jacket,  locking  hoop,  breech  hoop,  and  clip.  There  are  six  slightly 
varying  types  of  this  gun,  but  the  variations  deal  only  with  the 
manner  of  attachment  of  the  jacket  and  locking  hoop  and  do  not 
affect  the  general  dimensions.  The  gun  is  guided  in  recoil  by  two 
flanges  q|i  the  lower  side  of  the  jacket.  A  lug  on  top  near  the  for- 
ward en$  of  the  jacket  containing  a  T-slot  holds  the  forward  end  of 
the  recoil  cylinder. 

A  short  hoop  or  clip  is  shrunk  on  the  tube  near  the  muzzle  and  has 
on  its  underside  two  lugs  which  form  guides  for  the  gun  on  the 
cradle.  Provision  has  been  made  to  prevent  dust  from  entering  be- 
tween the  surfaces  of  the  guides  and  their  bearing  surfaces  on  the 
cradle. 

The  breech  ring,  which  screws  to  the  rear  end  of  the  jacket,  forms 
a  housing  for  the  breech  block  which  slides  up  and  down  with  the 
action  of  a  wedge.  The  ring  carries  at  the  top  a  lug  to  which  the 
hydraulic  recoil  cylinder  is  secured,  and  at  the  bottom  another  to 
which  the  two  spring  piston  rods  are  attached. 

The  breech  block  is  of  the  drop-block  type  and  operates  semi- 
automatically,  in  that  the  breech  closes  automatically  when  a  round 
of  ammunition  is  inserted.  It  is  opened  by  pulling  back  a  handle  on 
the  right  side  of  the  breech,  which  not  only  slides  the  breech  block 
out  of  place  but  operates  the  extractor,  thus  ejecting  the  empty  car- 
tridge case.  When  a  round  is  inserted  smartly  into  the  breech,  its 
rim  strikes  against  the  lips  of  the  extractor  causing  the  mechanism  to 
close  under  the  action  of  the  closing  spring.  The  cartridge  primer  is 
fired  from  the  left  side  of  the  carriage  by  a  continuous-pull  firing 
mechanism.  The  firing  pin  is  cocked  and  fired  by  one  continuous 
backward  motion  of  the  firing  handle. 

The  carriage  is  of  the  split-trail  type  which  means  that  the  trail  is 
made  up  of  two  halves,  each  being  hinged  to  the  axle  near  the  wheels 
and  capable  of  being  spread  out  at  a  wide  angle  or  brought  together 
at  the  spade  ends  and  locked  for  traveling.  This  feature  permits 
greater  elevation  and  traverse  than  the  ordinary  type  of  trail  and 
reduces  the  necessity  of  shifting  the  trail  when  changes  in  deflection 
of  50  mils  or  more  are  desired. 

A  seat  is  provided  on  each  half  of  the  trail,  the  one  on  the  left  for 
the  gunner  who  operates  the  sights,  the  traversing  and  angle  of  site 
handwheels,  and  fires  the  piece,  and  the  one  on  the  right  for  a  can- 
noneer who  sets  off  the  range  and  angle  of  site  and  operates  the 
breech  mechanism. 

(75) 


77 

The  recoil  mechanism  is  of  the  hydro-spring  variable  recoil  type 
consisting  of  one  hydraulic  and  two  spring  cylinders  which  comprise 
the  recoil  and  counterrecoil  mechanisms.  On  account  of  the  high 
angles  of  elevation  at  which  this  gun  can  be  fired,  it  was  necessary 
to  design  a  variable  recoil  system  by  means  of  which  the  length  of 
recoil  of  the  gun  would  be  automatically  lessened  the  higher  the 
muzzle  is  elevated.  This  is  accomplished  by  means  of  a  valve  turn- 
ing in  the  cylinder  and  shutting  off  or  opening  a  number  of  holes,, 
proportional  to  the  elevation,  thus  making  the  resistance  to  the 
passage  of  the  oil  greater  or  less. 


GUN  AT  MAXIMUM   ELEVATION. 


The  angle  of  site  mechanism  consists  principally  of  a  rocker 
which  is  moved  by  two  handwheels,  one  on  each  side  of  the  gun. 
Movement  of  the  mechanism  causes  the  gun,  cradle,  elevating  mech- 
anism, and  sights  to  move  also,  they  being  connected  to  the  rocker. 
The  handwheel  on  the  left  or  gunner's  side  is  used  when  laying  for 
direct  fire,  or  in  other  words,  when  site  is  set  independent  of  range. 
The  angle  of  site  scale  is  graduated  in  mils.  All  settings  on  the 
angle  of  site  scale  are  set  off  above  or  below  the  300-mil  graduation, 
this  being  the  normal  setting  when  the  axis  of  the  bore  and  the 
target  are  in  the  same  horizontal  plane. 

The  elevating  mechanism  used  in  setting  the  range  is  mounted  on 
the  rocker,  and  therefore  independent  of  the  angle  of  site  mech- 
anism, the  gun  and  cradle  only  being  moved  upon  operation  of  the 
handwheel.  The  range  scale  is  graduated  in  meters. 

Band  brakes  are  used  on  this  carriage  and  are  operated  by  a  hand 
lever  in  rear  of  the  shield  when  in  b-^tterv  position  and  by  a  lever 
from  the  axle  seat  when  in  traveling  posiHon. 


78 


79 


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INTERMEDIATE  SHAFT  GEAR— - 

-5CEOWN  NUr 


TRAVERSING  8TOR 

.C93<&X  1. 8755TEEL  PIN.' 
TRAVERSING 

AZIMUTH  SCALE: 


-ANCLE  OF  SITE  BRACKET  COVERCUTT) 

^TRAVERSING  HAMDWHEEL  SHAFT. 

SRCXONti  NUT. 

LW70DBOLT; 

^^ANGLE  OF  SITE  BRACKET(L£FT) 
-StK  HANDY  OILER 

BOOV. 


isresra  caiNK  HEAD  GERMAN  SLVEI?  SCREWSL 

INSTOUCTION  PLATE  (TRAVERSINGj.-^'  CWkNK  PIN. 
.625  CROWN  NVT. 


—-TRAVERSING  WORM  SHAFT  BEARING. 

1.812(1  $  STUD. 
-i  CROWN  NUT. 

TRAVERSING  WORM  SHAFT. 

TRAVERSING  WORM  (HINDLEY) 

I -TOP  CARRIAGE. 

HALF  BUSHINGi,T5«VECraP  CARRIAGE) 


.125  x  .75  STEEL  PIN.-1          \  \  x ADJUSTING  NUT. 

WASHERH   ^-.125x1.75  SPLIT  PIN. 


75  M  M.GUN  CARRIAGE,  MODEL  OF  1916. 

TRAVERSING  MECHANISM. 


81 

The  gunner  and  cannoneers  are  protected  by  the  customary  shields 
and  apron. 

The  sight  used  is  of  the  model  of  1916  type,  which  provides  a  sup- 
port for  the  panoramic  sight  and  the  peep  sight. 

^Wooden  wheels,  56  inches  in  diameter,  with  steel  hubs  and  tires,  are 
used,  the  tires  being  3  inches  in  width.  These  wheels  are  interchange- 
able with  those  of  the  caissons  and  limbers. 

Fixed  ammunition  is  used  in  the  75-millimeter  field  guns  and  is 
made  up  of  either  common  shrapnel  or  common  steel  shell.  Shrapnel 
rounds  are  issued  with  the  projectiles  filled  and  fuzed;  the  shell 
rounds  are  issued  filled  but  not  fuzed  and  contain  an  adapter  with 
booster  charge. 

The  projectiles  average  in  weight:  Shrapnel,  16  pounds,  fuzed; 
shell,  12.3  pounds,  fuzed.  The  components  of  one  round  are  the 
cartridge  case  with  primer,  powder  charge,  projectile,  and  fuze  in 
shrapnel,  and  adapter  and  booster  in  the  shell.  Weight  of  powder 
charge  is  approximately  1.5  pounds. 


CARRIAGE   AND   LIMBER  IN   TRAVELING   POSITION. 

A  battery  of  75-millimeter  gun  carriages,  model  of  1916,  is  accom- 
panied by  the  following  vehicles: 

75-millimeter  gun  carriage  limber,  model  of  1918. 

75-millimeter  gun  caisson,  model  of  1918. 

75-millimeter  gun  caisson  limber,  model  of  1918. 

Forge  limber,  model  of  1902  MI. 

Store  limber,  model  of  1902  MI. 

Battery  and  store  wagon,  model  of  1917. 

Battery  reel,  model  of  1917.1 

Feel,  model  of  1909  MI. 

Cart,  model  of  1918.1 

The  above  gun  carriage  was  originally  the  3-inch  gun  carriageT 
model  of  1913,  which  was  later  called  the  3-inch  gun  carriage,  model 
of  1916.  The  gun  was  afterwards  modified  to  caliber  75  millimeters, 
as  was  the  3.3-inch  British,  thereby  permitting  interchangeability  of 
ammunition  with  the  French  guns. 

1  For  horse  batteries  the  battery  reel,  model  of  1917,  is  issued.  For  motorized  batteries 
the  reel,  model  of  1909  MI,  with  the  cart,  model  of  1918,  is  issued  in  lieu  of  the  battery 
reel,  model  of  1917. 


82 


75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1916  MI. 


A  number  of  75-millimeter  gun  carriages,  model  1916,  redesigned  to 
use  St.  diamond  hydropneumatic  recoil  mechanisms  in  place  of  th& 
hydrospring  type,  and  standard  75-millimeter  guns,  model  of  1916 
Mill,  modified  and  fitted  with  counter  weights,  are  available  for 
issue  to  the  service.  The  new  materiel  will  be  known  as  75-milli- 
meter gun  materiel,  model  of  1916  MI. 


LEFT   SIDE    VIEW    OF    CARRIAGE    IN    FIRING    POSITION. 

The  St.  diamond  mechanism  as  adopted  for  the  75-millimeter 
carriages  is  of  the  hydropneumatic  type  and  was  developed  in  1917 
by  Col.  Rimailho,  of  the  French  Army.  The  use  of  small  forg- 
ings  was  made  possible  by  introducing  high  pressures  in  the  recuper- 
ator and  recoil  cylinders.  In  order  to  hold  these  pressures,  special 
suitable  packings  had  to  be  used. 

Essentially  the  mechanism  consists  of  three  cylinders.  The  middle 
one  is  the  recoil  cylinder.  The  right  cylinder  has  an  air  reservoir  at  its 
forward  end  and  an  oil  reservoir  at  the  rear  end.  The  left  cylinder 
is  the  recuperator  cylinder,  having  at  its  forward  end  an  air  space, 
and  at  its  rear  end  a  regulator  for  controlling  the  length  of  recoil. 
The  floating  piston  in  this  cylinder  separates  the  air  from  the  oil. 

In  recoil  the  gun  moves  to  the  rear,  carrying  with  it  the  recoil  piston 
(middle  cylinder).  The  recoiling  parts  are  held  in  battery  by  the 
reaction  of  the  air  on  the  floating  piston,  which  is  transmitted  through 
the  liquid  against  the  leak-tight  recoil  piston.  The  energy  of  recoil 
is  absorbed  by  the  throttling  of  the  oil  through  a  spring-controlled 
orifice  in  the  regulator  valve. 

(83) 


84 


85 

An  opening  is  provided  between  the  recoil  and  the  recuperator 
cylinders  to  house  the  regulator  valve.  During  recoil  the  pressure  in 
the  recoil  cylinder  opens  the  regulator  valve,  the  movement  of  which 
is  controlled  by  a  helical  spring  and  a  number  of  Belleville  springs. 
The  oil  passing  through  the  orifice  controlled  by  this  valve  moves  the 
floating  piston  forward  against  the  air  pressure,  thereby  storing  up 
energy  to  return  the  gun  from  the  recoiled  position  to  its  position  in 
battery.  The  valve  in  the  counterrecoil  orifice  remains  closed  during 
recoil. 

Throttling  during  recoil  is  controlled  by  the  regulator  valve  con- 
sisting of  an  upper  and  lower  valve  stem.  The  lower  valve  stem  is 
seated  in  a  circular  seat  at  the  entrance  channel  to  the  valve.  As  the 
valve  lifts,  the  throttle  area  becomes  the  vertical  circumferential 


RIGHT   SIDE   VIEW   OF   CARRIAGE  IN   BATTERY   POSITION. 

area  between  the  valve  and  its  seat.  In  long  recoil  the  movement  of 
the  valve  is  controlled  by  a  spiral  spring  which  reacts  on  the  lower 
valve  stem.  The  upper  stem  rests  in  a  valve  housing  and  has  Belle- 
ville springs  reacting  on  the  stem  only.  To  move  the  upper  valve 
stem,  the  whole  housing  is  lowered  automatically  by  a  cam  operated 
when  the  cradle  is  elevated.  At  short  recoil  the  upper  stem  of  this 
regulator  is  brought  down  by  the  cam  until  its  lower  surface  is  in 
contact  with  the  top  surface  of  the  lower  valve  stem,  thus  controlling 
the  throttling  of  the  valve. 

The  regulator  valve  is  closed  during  the  counterrecoil  movement 
except  for  a  very  small  constant  opening.  During  counterrecoil  there 
is  also  a  second  path  for  the  flow  of  oil  through  a  small  channel 
beginning  at  the  inside  end  of  the  buffer  chamber  in  the  recuperator 
cylinder  and  finally  emptying  in  the  recoil  cylinder  through  a  by-pass 
around  the  regulator  valve.  Near  the  end  of  counterrecoil  the  taper- 


86 

ing  buffer  rod  on  the  floating  piston  in  the  recuperator  controls  the 
flow   through   the    second   path   by    causing   additional   throttling 


through  the  small  annular  arc  between  the  buffer  chamber  and  buffer 
rod,  thus  bringing  the  recoiling  parts  to  rest  without  any  great 
amount  of  shock. 


75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1897  MI. 

(FRENCH). 


The  French  75-millimeter  field  gun  adopted  for  the  service  of  the 
United  States  dates  back  to  1897,  when  it  was  perfected  by  the 
French  Army. 

The  French  model  1897  field  gun  has  fired,  on  test,  as  high  as  30 
shots  in  a  minute.  This  rate  is  probably  as  high  as  can  be  reached 
by  any  nonautomatic  75  gun.  Apart  from  the  personnel  service  to 
the  piece,  the  length  of  time  which  a  gun  could  maintain  this  rate 
of  fire,  or  any  other  rapid  rate  of  fire,  is  perhaps  not  definitely  de- 
termined. As  to  whether  or  not  such  length  of  time  would  be 
limited  by  the  heating  of  the  gun  or  by  the  heating  of  the  recoil 
mechanism  depends  upon  the  construction. 

Rapidity  of  fire  is  of  vital  importance,  for  it  is  self-evident  that 
under  certain  conditions  a  gun  which  can  fire  twice  as  many  shots 
per  minute  as  some  other  gun  is,  for  the  moment,  equivalent  to  two 
guns  of  the  second  class.  Rapidity  of  firing  action  is  dependent 
upon  the  arrangements  involved  for  the  sighting,  maintaining  of  the 
gun  on  its  range,  loading,  firing,  time  of  recoil  and  return  of  the  gun 
to  battery  position,  opening  of  the  breech,  and  ejection  of  the  empty 
cartridge  case. 

For  artillery  of  position  a  great  part  of  the  enormous  energy  re- 
quired to  start  the  projectile  on  its  way  may  be  absorbed  by  a  heavy 
foundation  furnished  as  a  mounting  for  the  piece.  An  efficient  recoil 
mechanism  is,  however,  of  vital  importance  in  connection  with  light 
artillery  for  field  service,  owing  to  the  essentially  light  weight  of  the 
carriage  on  which  the  gun  is  mounted,  to  permit  of  its  ready  mobility. 

The  recoil  mechanism  not  only  absorbs  the  greater  part  of  the 
recoil  energy  of  the  gun  but  it  returns  the  gun  to  the  battery  or 
firing  position,  and  to  be  efficient  it  must  be  able  to  perform  these  two 
functions  quickly,  smoothly,  surely,  and  continuously.  The  wrord 
"surely"  is  used  in  the  sense  of  firmly  and  without  shock,  and  of 
being  reliable.  The  recoil  mechanism  not  only  takes  up  the  recoil 
but  it  forces  the  gun  all  the  way  back  into  battery,  or  to  a  position 
within  the  variation  which  the  design  permits,  under  all  conditions 
of  elevation  and  heating. 

(87) 


88 


89 

The  general  theory  of  hydropneumatic  recoil  mechanism  is  not  new. 
In  its  relation  to  light  artillery  its  most  notable  exemplification  in 
battle  has  appeared  in  the  Puteaux  Arsenal  type  used  with  the 
French  75  piece.  Its  virtues  have  been  widely  heralded  and  every 
effort  has  been  made  to  keep  its  construction  secret.  Its  several 
parts  were  manufactured  at  different  points  in  France  and  these 
were  assembled  in  a  central  establishment,  where  but  few  persons 
were  admitted  to  this  room.  In  the  agreement  to  manufacture  the 
complete  recuperator  in  the  United  States,  it  was  stipulated  that  the 
greatest  secrecy  should  be  maintained  with  reference  to  its  design, 
manufacture,  and  assembly. 

There  is  a  difference  between  land  and  naval  warfare,  in  this 
respect:  In  a  duel  between  two  large  fighting  ships  of  equal  speed 
to  insure  their  remaining  in  contact,  the  one  with  the  heavy,  long- 
range  guns  has  the  other  at  its  mercy,  as  it  can  destroy  both  its  oppo- 
nent's base  and  at  the  same  time  its  opponent's  personnel  by  sinking 
the  opponent  ship.  In  a  land  battle,  the  fortifications  may  be  reduced 
by  the  long-range  gun,  of  heavy  caliber,  but  it  is  the  destruction  or 
capture  of  personnel  which  brings  a  war  to  an  issue  and  the  personnel 
may  move  to  open  country  and  open  order,  under  which  conditions 
the  heavy,  long-range  gun,  which  is  expensive  to  construct,  slow  and 
difficult  to  transport,  expensive  to  fire,  and  withal  short  of  life,  no 
longer  has  a  great  target  on  which  its  tremendous  energy  may  be 
concentrated. 

Land  warfare  has  clearly  demonstrated  that  it  is  the  killing  and 
disabling  of  personnel  or  the  capture  of  enemy  troops  in  large  num- 
bers which  far  outweighs  the  capture  of  cities  or  of  terrain  which 
is  nonproductive  of  raw  material,  in  the  forcing  of  an  issue.  This 
To-millimeter  gun  was  most  effective  in  the  open-country  fighting,  in 
the  protection  of  troops,  and  in  working  havoc  among  enemy  troops 
and  bringing  in  prisoners  by  creeping  barrage  laid  behind  an  enemy 
formation. 

Weights,  dimensions,  and  ballistics. 

Caliber millimeters—  75 

Total  weight  of  gun  and  breech  mechanism pounds 1,  015 

Total   length   of  gun inches—  107,125 

Rifling,  uniform,  right  hand,  1  turn  in  25.6  calibers. 
Muzzle  velocity : 

Shell  (short  fuze) feet  per  second 1,955 

Shell    (long   fuze) do 1,930 

Shrapnel do 1,  755 

Maximum  range: 

Shell    (short   fuze)     (Mark   IV    shell) yards—  8,640 

Shell    (long  fuze) do 9,350 

Shrapnel— do 7,  .440 


90 


91 

Weight  of  complete  round  of  ammunition : 

Shrapnel pounds 16 

Shell . do 12.  3 

Diameter  of  steel  tired  wheels inches 52.  5 

Width    of   track do 59.  68 

Length  of  recoil  of  gun  on  carriage do 44.  9 

Height  of  axis  of  gun  from  ground do 40.  4 

Maximum  angle  of  elevation degrees 19 

Maximum   angle  of  depression do 10 

Total  traverse  of  carriage  on  axle do 6 

Weight  of  the  carriage,  complete  (without  gun) pounds__  1,642 

Weight  of  gun  and  carriage,  fully  equipped 2,657 

75-MILLIMETER    GUN    AND    CARRIAGE,    MODEL    OF    1897    MI 

(FRENCH). 

The  gun  is  of  the  built-up  construction  type,  consisting  mainly  of 
a  steel  tube  reinforced  at  the  breech  end  with  a  breech  hoop  and 
covered  in  the  central  portion  with  a  bronze  jacket.  The  total 
length  from  face  of  breech  to  muzzle  is  slightly  less  than  nine  feet. 

The  recoil  lug  under  the  breech  carries  the  coupling  key,  which 
connects  the  gun  to  the  recoil  mechanism.  A  safety  pin  operates 
between  the  breechblock  and  the  coupling  key,  so  that  it  is  impossible 
to  close  the  breech  and  fire  the  gun  when  it  is  not  securely  locked 
to  the  recoil  mechanism  of  the  carriage. 

On  the  underside  of  the  gun  are  inclined  bronze  slides  which  are 
in  contact  with  similar  slides  on  the  recoil  mechanism.  Rollers 
are  also  attached  to  the  gun,  and  during  recoil  the  gun  first  slides  on 
the  inclined  guides  and  then  the  rollers  lift  the  weight  off  the  slides, 
the  remainder  of  the  travel  being  on  the  rollers.  A  pair  of  rollers 
at  the  muzzle  permit  a  long  recoil  with  short  guides  by  taking  the 
overhanging  weight  when  the  gun  is  at  full  recoil. 

The  breechblock  is  of  the  Xordenfeld  type,  cylindrical  in  shape  and 
threaded  on  the  outside.  It  is  opened  or  closed  by  the  operating 
handle  from  the  right  side  of  the  gun  by  the  same  man  who  sets  the 
gun  for  range  and  fires  the  piece.  Opening  the  breech  automatically 
actuates  the  extractor,  which  in  turn  ejects  the  empty  cartridge  case. 
The  round  of  ammunition  is  fired  by  a  striker  which  is  driven  for- 
ward by  a  spring-actuated  hammer  pulled  by  the  lanyard. 

The  carriage  is  very  compact  and  simple,  consisting  of  a  housing 
around  the  axle,  above  which  is  the  support  for  the  cradle,  and  a 
box  section  trail  ending  with  the  customary  spade  and  lunette. 
Seats  are  provided  for  two  men,  the  one  sitting  on  the  right  side 
operating  the  range  scale  mechanism,  opening  or  closing  the  breech 
and  firing  the  piece ;  the  man  on  the  left  sighting  the  gun  and  oper- 
ating the  angle  of  site  and  traversing  mechanisms. 

The  recoil  mechanism  is  of  the  hydropneumatic,  long  recoil  type 
and  contains  both  recoil  and  counterrecoil  mechanisms.  A  gage 


92 


93 


94 

plunger  is  located  in  the  rear  end  of  the  cradle  which,  when  flush, 
indicates  that  more  oil  should  be  added  until  the  plunger  projects 
about  f  inch.  Oil  may  l?e  added  by  forcing  it  through  a  valve  in  the 
side  of  the  cradle  by  a  hand  screw  filler,  or  by  means  of  a  portable 
battery  pump  clamped  to  the  side  of  the  trail  and  connected  through 
the  trunnions  to  the  interior  of  the  cradle. 

The  recoil  mechanism  is  housed  inside  of  the  cradle,  through  which 
are  bored  an  upper  and  lower  cylinder,  filled  with  Oleonapthe,  and 
connected  together  by  means  of  a  passageway  provided  for  that 
purpose.  The  air  in  the  front  part  of  the  upper  cylinder  (in  front  of 
the  piston)  is  free  to  communicate  with  the  outside  air  through  a 
plug,  but  the  forward  end  of  the  lower  cylinder  is  closed  and  con- 


LEFT   SIDE   VIEW   OF   CARRIAGE. 

tains  compressed  air  at  approximately  150  kilograms  per  square 
centimeter  (1,833.5  pounds  per  square  inch). 

In  the  upper  cylinder  a  piston  is  permitted  to  move,  the  piston 
rod,  however,  being  secured  to  the  gun.  The  lower  cylinder  is 
fitted  with  a  pipe,  at  the  end  of  which  is  a  circular  ring,  this  pipe 
being  screwed  in  the  rear  part  of  the  cylinder  where  the  valves  are 
housed.  A  diaphragm  equipped  with  a  hollow  rod,  also  a  floating 
piston  fitted  with  a  small  rod,  are  incorporated  in  the  lower  cylinder. 

During  recoil  the  piston  of  the  upper  cylinder  compresses  the 
liquid,  forcing  it  to  pass  through  various  valves,  also  openings 
formed  between  the  pipe  and  the  hollow  rod  of  the  diaphragm.  The 
passing  of  the  liquid  through  these  different  openings  constitutes  the 
braking.  In  so  moving,  the  liquid  opens  the  valves  (which  are  opened 


95 


551  GO— 21 7 


97 

wide  at  the  beginning  of  the  recoil  and  gradually  close  in  propor- 
tion to  the  decrease  of  the  speed  of  the  recoil).  At  the  same  time, 
the  air  in  the  lower  cylinder  is  compressed  by  the  action  of  the 
liquid  on-  the  diaphragm.  To  return  to  battery  at  the  end  of  the 
recoil,  the  compressed  air  forces  the  diaphragm  back.  The  liquid 
thus  compressed  acts  directly  on  the  upper  cylinder  piston,  causing 
it  to  return  to  its  initial  position. 

The  interior  of  the  recoil  mechanism  was  maintained  confidential 
by  the  French  Government  before  and  during  the  war,  and  when  its 
manufacture  was  taken  over  by  the  Ordnance  Department,  agree- 
ment was  made  to  continue  the  secrecy  of  these  parts.  Very  fine 
adjustments  are  made  when  the  parts  are  assembled,  and  conse- 
quently no  repairs  or  adjustments  are  permitted  to  be  made  in  the 
field.  The  complete  recoil  mechanism  must  be  sent  to  special  repair 
depots  for  repairs.  The  recoil  mechanism  will  function  properly 
without  the  operating  personnel  understanding  the  interior  mech- 
anism. 

The  angle  of  site  mechanism  consists  of  a  handwheel  and  gears, 
and  provides  for  elevating  or  depressing  a  rocker  13  degrees  with 
reference  to  the  trail.  The  rocker  fits  around  the  trunnions  and 
has  a  segment  of  a  gear  which  meshes  with  the  elevating  pinion. 
To  the  rocker  is  secured  an  elevating  screw  and  nut  which  connects 
with  the  cradle.  In  setting  the  angle  of  site,  the  rocker  is  set  in 
motion,  thereby  moving  the  cradle  and  gun.  The  angle  of  site  mecha- 
nism is  also  called  the  independent  line  of  sight;  because  the  range 
setting  is  independent  of  the  setting  of  the  angle  of  site  which  is  done 
by  the  angle  of  site  handwheel. 

The  range  scale  mechanism  which  operates  the  elevating  screw 
provides  an  elevation  of  12  degrees  to  give  the  correct  range  and  is 
obtained  by  movement  of  the  cradle  in  reference  to  the  rocker. 

The  circular  scale  graduated  in  meters  indicating  the  range  is 
mounted  on  the  side  of  the  cradle  and  through  gearing  is  connected 
to  the  elevating  screw.  A  range  rack  is  connected  to  the  rocker 
arm  which  is  also  graduated  in  meters.  On  carriages  made  in 
America  an  extra  strip  is  placed  alongside  the  range  rack  and  is 
graduated  in  mils.  The  range  scales  are  graduated  up  to  5,500 
meters,  but  greater  ranges  can  be  obtained  by  burying  the  trail, 
and  thus  giving  higher  angles  of  elevation.  Interference  of  the 
breech  against  the  trail,  however,  limits  the  total  possible  elevation 
obtainable  by  combination  of  the  elevation  due  to  the  angle  of  site 
and  that  due  to  range  to  19  degrees. 

On  this  carriage  axle  traverse  is  used.  A  geared  nut,  held  inside 
of  the  axle  housing,  rotates  around  the  axle  which  is  threaded  with 
a  coarse  rectangular  thread.  Movement  of  this  nut  forces  the 


98 

carriage  to  the  right  or  left,  pivoting  around  the  spade,  one  wheel 
advancing  and  the  other  backing  up.  Traverse  is  about  three  degrees 
right  and  three  degrees  left. 

A  combination  road  brake  and  firing  support  is  hung  around  the 
axle,  permitting  the  application  of  brake  shoes  against  the  tires 
of  the  wheels  when  traveling,  and  the  lowering  of  the  framework  to 
<he  ground  and  the  mounting  of  the  wheels  thereon,  for  firing.  This 
last  operation  is  called  abatage,  the  three  steps  being  indicated  in  the 
following  figures : 


POSITION      I  POSITION     2.  POSITION    3 

ABATAGE      POSITION 

Wooden  wheels.  1,334  millimeters  (52.5  inches)  diameter,  are  used, 
and  have  steel  tires  3.5  inches  wide.  These  wheels  are  interchange- 
able with  the  French  limber  wheels,  but  not  with  the  American 
limber  or  caissons  for  the  75-millimeter  gun  carriages. 

The  customary  shield  and  apron  protects  the  gunners  when  under 
fire. 

The  sight,  model  of  1901  (French),  includes  the  collimating  sight, 
angle  of  site  level,  and  angle  of  site  scale.  It  is  mounted  on  the 
left  side  of  the  rocker,  at  the  trunnions.  It  has  no  telescopic  features 
and,  therefore,  its  range  is  limited.  An  auxiliary  angle  of  site  level 
is  furnished  to  replace  the  regular  level  and  gives  an  additional  200 
mils  for  use  in  hilly  or  mountainous  country. 

Fixed  ammunition  is  used  in  this  75-millimeter  field  gun  and  is 
made  up  with  either  common  shrapnel  or  common  steel  shell.  Shrap- 
nel rounds  are  issued  with  the  projectiles  filled  and  fuzed:  the  shell 
rounds  are  issued  filled  but  not  fuzed,  and  contain  an  adapter  with 
booster  charge. 

The  projectiles  average  in  weight:  Shrapnel,  16  pounds,  fuzed; 
shell,  12.3  pounds,  fuzed.  The  components  of  one  round  are  the 
cartridge  case,  with  primer;  the  powder  charge;  projectile;  and 
fuze,  in  shrapnel:  and  adapter  and  booster  in  the  shell. 


99 


100 


101 

75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1897  MI  (FRENCH). 

A  battery  of  75-millimeter  gun  carriages,  model  of  1897  MI 
(French),  is  accompanied  by  the  following  vehicles: 

75-millimeter  gun  and  carriage,  model  of  1897  MI.  * 

75-millimeter  gun  carriage  limber,  model  of  1918. 

75-millimeter  gun  caisson,  model  of  1918. 

75-millimeter  gun  caisson  limber,  model  of  1918. 

Battery  and  store  wagon,  model  of  1917. 

Forge  limber,  model  of  1902  MI. 

Store  limber,  model  of  1902  MI. 

Battery  reel,  model  of  1917.1 

Keel,  model  of  1909  MI.1 

Cart,  model  of  1918.1 

The  gun  and  carriage  are  of  French  design,  and  of  both  French 
and  American  manufacture.  The  accompanying  vehicles  are  all  of 
American  design  and  manufacture. 

1  For  horse  batteries  the  battery  reel,  model  of  1917,  is  issued.  For  motorized  batteries, 
Che  reel,  model  of  1909  MI,  with  the  cart,  model  of  1918,  is  issued  in  lieu  of  the  battery 
reel,  model  of  1917. 


102 


75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1917 

(BRITISH). 


The  75-millimeter  gun,  model  of  1917  (British),  was  originally 
known  as  the  18-pounder,  but  was  modified  by  adapting  it  to  the  75- 
millimeter  caliber  materiel.  This  weapon  is  equipped  with  customary 
unit  trail ;  the  interference  of  the  trail  with  the  breech  limits  the  gun 
elevation.  With  the  split  trail,  the  breech  can  pass  down  into  the 
V  formed  by  separating  the  two  sections  of  the  trail.  The  theoretical 
elevation  for  obtaining  maximum  range  under  ideal  ballistic  condi- 
tions is  45°  from  the  horizontal,  and  is  actually  some  few  degrees  less 


FRONT   VIEW   OF   CARRIAGE. 

than  this.  Increased  range  is  sometimes  obtained  with  field  guns 
whose  normal  elevation  is  limited  by  setting  the  axles  or  wheels  on 
raised  surfaces,  or  by  sinking  the  trail  below  the  level  of  the  wheels, 
for  the  purpose  of  pointing  the  gun  at  an  elevation  higher  than  the 
mechanical  arrangement  of  the  carriage  permits.  This  is,  however, 
a  subterfuge,  limited  in  its  practical  application. 

The  American  model  1916  split-trail  carriage  permits  great  eleva- 
tion within  the  mechanism  of  the  carriage  and  likewise  a  wide 
traverse  without  changing  the  position  of  the  trail.  The  recoil 

(103) 


104 


105 


mechanism  on  the  1916  model  was  adapted  to  the  higher  permissible 
elevation  of  the  gun,  and  was  supplied  with  a  variable  recoil,  auto- 
matically adjusted  to  different  elevations.  The  ability  to  outrange 
the  enemy  is  an  attainment  constantly  being  sought,  and  therefore 
high  elevation  and  reduction  of  resistance  of  the  projectile  passing 
through  air  are  the  means  through  which  it  was  hoped  to  obtain  the 
increased  range  desired.  Likewise,  a  wide  horizontal  arc  of  fire, 
without  resetting  of  the  trail  and  consequent  resetting  of  the  sight- 
ing devices,  is  a  great  convenience  and  saver  of  time. 

As  compared  with  the  British  model  1917,  the  American  3-inch 
model  of  1902  carriage  permits  of  a  maximum  angle  of  elevation  of 


REAR  VIEW  OP  CARRIAGE. 

15°,  depression  of  5°,  and  traverse  of  142  mils,  while  the  British 
model  permits  16°  elevation,  5°  depression,  and  142  mils  traverse. 
The  French  model  1897  carriage  permits  a  maximum  angle  of  eleva- 
tion of  19°,  depression  10°,  and  traverse  106  mils.  The  American 
model  1916  carriage  allows  a  total  vertical  movement  of  from  53° 
elevation  to  7°  depression,  and  a  traverse  of  800  mils  (an  artillery 
mil  equals  the  angle  subtended  by  -g-jVff  °^  the  circumference  of  a 
circle).  The  American  model  1902  carriages  are  arranged  with  a 
hydro-spring  recoil  mechanism,  and  so  is  the  British  model  1917  and 
the  American  model  1916.  The  French  model  1897  carriage  is 
equipped  with  a  hydro-pneumatic  recoil  mechanism. 

The  basic  difference  in  the  recuperator  or  recoil  mechanism  of  the 
French  model  1897  gun,  as  compared  with  the  British  model  and  the 


106 

American  model,  lies  in  the  fact  that  the  French  model  involves  the 
principle  of  oil  and  compressed  air  for  absorbing  the  recoil  of  the  gun 
and  returning  it  to  battery  or  firing  position,  and  is  practically  self- 
contained  in  one  large  heat-treated  steel  forging,  with  a  system  of 
finely  fitted  surfaces  and  adjustment  valves;  while  in  the  British  and 
American  model  recoil  mechanism,  oil  and  steel  springs,  instead  of 
compressed  air,  are  employed,  with  a  combination  of  pistons  and  steel 
tubing. 

A  reference  may  also  be  made  relative  to  the  desirablity  of  single 
or  unit  trails  as  compared  with  the  split  trail.  The  latter  allows  of 
greater  traverse,  but  as  a  new  objective  makes  necessary  a  resetting 
of  the  trail,  the  change  in  setting  requires  much  more  time  than  with 
the  unit  trail.  The  split  trail  is  heavier  and  the  equalizing  mecha- 
nism, necessary  to  the  proper  distribution  of  recoil  shock  to  both  trail 
sections,  establishes  a  relative  movement  between  the  two  trail  sec- 
tions, with  the  result  that  the  split  trail  can  be  set  up  less  quickly 
than  the  unit  trail  on  uneven  ground. 

Weight,  dimensions  and  ballistics. 

Caliber Millimeters—  75 

Weight  of  gun  and  breech  mechanism pounds 995 

Total  length  of  gun inches—  88.21 

Length  of  bore do 83.915 

Rifling,  right-hand  twist,  zero  turns  at  origin  to  1  turn  in  75  inches  at 
9.72  inches  from  muzzle,  thence,  iiniform. 

Number   of   grooves 24 

Muzzle  velocity : 

Shrapnel feet  per  second--  1,693 

Shell    (short  fuse) do 1,900 

Shell  (long  fuse) _— do 1,876 

Maximum  range: 

Shrapnel    (Mark  IV  shell) yards__  6,464 

Shell  (short  fuse) do 8,100 

Shell   (long  fuse) do 7,450 

Weight  of  one  round  of  ammunition : 

Shrapnel pounds 16 

Shell do ]2.3 

Weight  of  carriage  complete  (without  gun) do 1.  950 

Weight  of  gun  and  carriage  in  battery  position do 2,  890 

Diameter  of  wheel* inches 56 

Width  of  track do 60 

Length  of  recoil  of  gun  on  carriage  (normal) do 45 

Length  of  recoil  of  gun  on  carriage  (maximum) do 49 

Height  of  axis  from  ground do 38.  80 

Maximum  angle  of  elevation degrees 16 

Maximum  angle  of  depression do 5 

Maximum  traverse,  each  side  of  center mils 72 

Weight   of  gun,   carriage,   and   limber    (British)    fully   equipped,   also 

loaded  with  shrapnel  and  fuse  boxes pounds 4,591 

Weight  of  gun,  carriage,  and  limber   (American)    fully  equipped,  also 
loaded  with  shrapnel  and  fuse  boxes pounds 4,458 


107 


V\\l  I!'//'  /////; 
\\\l' I/ ///////.// 

1  i!    i;  ill 


108 


109 

75-MILLIMETER  GUN  AND  CARRIAGE,   MODEL   OF  1917   (BRITISH). 

The  gun  is  built  up  of  alloy  steel,  consisting  of  a  tube,  a  series  of 
layers  of  steel  wire,  a  jacket,  and  a  breech  ring.  The  tube  extends 
from  the  rear  end  of  the  chamber  to  the  muzzle.  Over  the  rear  por- 
tion of  the  tube  are  wound  15  layers  of  steel  wire.  The  jacket  is 
fitted  over  the  exterior  of  the  tube  and  wire,  and  is  secured  longitu- 
dinally by  corresponding  shoulders  and  the  breech  ring,  which  is 
screwed  over  the  jacket  at  the  rear  and  secured  by  a  set  screw.  The 
breech  ring  is  prepared  for  the  reception  of  the  breech  mechanism, 
and  is  provided  on  the  upper  side  with  a  lug  for  the  attachment  of 
the  hydraulic  buffer.  Longitudinal  projections  on  each  side  of  the 
jacket  form  guides  for  the  gun  when  in  the  cradle  of  the  carriage. 
A  plane  for  a  clinometer  is  prepared  on  the  upper  surface  of  the 
breech  ring.  Vertical  and  horizontal  axis  lines  are  cut  on  the  face 
of  the  muzzle  for  use  in  verifying  the  adjustments  of  the  sight. 

The  breech  block  is  of  the  interrupted  screw  type  having  two 
threaded  and  two  slotted  sectors.  The  breech  recess  of  the  gun  is 
slotted  and  threaded  to  correspond  with  the  threads  on  the  block  and 
the  latter  is  screwed  to  a  cylindrical  section,  or  carrier,  which  is  hinged 
to  the  right  side  of  the  breech.  Hinged  to  the  rear  face  of  the  carrier 
is  a  hand  lever,  provided  with  bevel  teeth  which  engage  with  corre- 
sponding teeth  on  the  rear  face  of  the  breech  block,  so  arranged  that 
when  the  lever  is  pulled  to  the  right,  the  first  movement  of  the  lever 
unlocks  the  breech  block,  and  on  continuing  the  motion  the  block 
and  carrier  are  swung  into  the  loading  position.  The  breech  is 
opened  by  the  cannoneer  on  the  right  seat  pulling  the  hand  lever 
toward  him.  The  extractor,  hinged  to  the  right  side  of  the  breech, 
is  automatically  actuated  in  opening  the  breech,  thus  ejecting  the 
empty  cartridge  case. 

The  -firing  mechanism  is  so  arranged  that  the  gun  can  not  be  fired 
before  the  breechblock  is  home  and  the  hand  lever  locked,  and  is 
known  as  a  continuous-pull  mechanism.  By  means  of  the  firing 
lever  on  the  left  side  of  the  gun,  operated  by  the  gunner,  the  firing 
pin,  which  seats  in  an  axially  bored  hole  in  the  breechblock,  is  cocked 
and  fired  by  one  continuous  backward  motion  of  the  lever. 

The  carriage  has  a  tubular  steel  trail  and  axle,  the  rear  end  of  the 
trail  being  fitted  with  a  spade,  lifting  handles,  trail  eye,  and  traversing 
lever.  The  top  carriage  is  provided  with  bearings,  by  means  of  which 
it  is  pivoted  on  the  axle  for  traversing.  Bearings  are  provided  at 
the  top  to  receive  the  cradle  trunnions  on  which  the  cradle  pivots. 
Longitudinal  recesses  are  cut  in  the  inner  surface  of  the  lower  portion 
of  the  cradle  for  the  reception  of  the  guides  on  the  jacket  of  the  gun. 

A  seat  is  provided  on  the  left  side  of  the  trail  for  the  gunner  who 
sets  the  sights  and  fires  the  gun,  and  one  on  the  right  for  a  cannoneer 
who  sets  the  range  and  operates  the  breech. 


110 

The  customary  top  and  main  shields  and  the  apron  are  provided 
for  the  protection  of  the  personnel  against  gun  fire. 

The  recoil  cylinder  is  contained  in  the  spring  case  in  the  upper  por- 
tion of  the  cradle  and  is  surrounded  by  two  sets,  inner  and  outer,  of 
four  sections  each,  of  counterrecoil  (running-out)  springs,  these 
being  held  under  initial  compression  between  an  external  flange  on. 
the  front  end  of  the  recoil  cylinder  and  an  internal  flange  at  the  rear 
end  of  the  outer  spring  case.  The  cylinder  is  attached  and  secured  to 
the  rear  end  of  the  gun  by  two  nuts,  while  the  piston  rod  with  piston, 
which  fits  inside  of  the  cylinder,  is  secured  to  the  forward  end  of  the 
spring  case.  The  piston  rod  is  bored  out  for  the  reception  of  the 
counterrecoil  buffer  which  is  secured  in  the  rear  end  of  the  cylinder. 

Upon  being  fired  the  gun  recoils,  carrying  with  it  the  recoil  cylin- 
der. The  oil  is  forced  to  pass  from  in  front  of  the  stationary  piston 
to  the  rear  through  grooves  of  graduated  depth  which  set  up  an 
hydraulic  resistance,  thus  checking  the  energy  and  bringing  the  gun 
to  rest.  In  recoiling,  the  gun  further  compresses  the  two  sets  of 
springs  which,  after  the  gun  has  reached  its  maximum  recoil,  cause 
it  to  return  to  battery.  The  counterrecoil  buffer  displaces  the  liquid 
in  the  rear  end  of  the  piston  rod,  the  liquid  being  forced  to  escape 
over  the  tapered  flats,  thus  resulting  in  the  gun  returning  to  battery 
without  shock. 

A  gravity  tank  is  bolted  to  the  front  end  of  the  recoil  mechanism, 
which  insures  the  cylinder  being  constantly  filled,  and  is  protected 
from  gun  fire  by  a  shield. 

The  angle  of  sight  level  is  carried  on  a  bracket  riveted  to  the  under- 
side of  the  rocking  bar  at  the  rear  end  and  is  adjusted  by  a  leveling 
screw  to  which  is  attached  a  micrometer  disc  for  setting  off  the  angle 
of  sight. 

The  range  indicator  is  fitted  to  the  right  side  close  to  the  handwheel 
and  consists  of  a  meter  scale  ring  graduated  on  its  face  in  hundreds 
of  meters,  the  periphery  of  the  ring  being  graduated  in  mils.  The 
mechanism  allows  an  elevation  of  16°  and  depression  of  5°. 

The  elevating  gear  is  divided  into  two  portions,  upper  and  lower, 
and  so  arranged  that  the  gun  may  be  elevated  or  depressed  without 
altering  the  line  of  sight. 

The  traversing  gear  is  pivoted  to  a  bracket  fastened  to  the  trail  at 
the  rear  end  of  the  top  carriage,  and  is  operated  by  a  handwheel 
extending  out  to  the  left  side  by  means  of  which  the  gun  may  be 
traversed  72  mils  right  or  left  from  center.  A  scale  strip  and  pointer 
indicate  the  angle  of  traverse. 

Wooden  wheels,  56  inches  in  diameter,  are  used,  having  steel  tires 
3  inches  in  width.  Drag  washers  free  to  rotate  about  the  hubs  are 
secured  by  the  dust  caps. 


Ill 


55160—21- 


112 


113 

The  tire  brake  is  for  use  in  traveling,  and  is  always  used  when 
firing.  Brake  arms  are  pivoted  at  one  end  to  a  bracket  on  the  trail 
and  have  at  their  other  end  a  cast-iron  brake  shoe  which  acts  upon 
the  tire  of  the  wheel.  The  braking  action  is  adjustable  and  brakes 
are  operated  by  a  lever  having  an  eccentric  link  at  its  end. 

The  sights  used  are  the  rocking-bar  sight  and  panoramic  sight, 
model  of  1917,  which  are  located  tm  the  left  side  of  the  carriage. 

Fixed  ammunition  is  used  in  this  75-millimeter  field  gun  and  is 
made  up  of  either  common  shrapnel  or  common  steel  shell.  Shrap- 
nel rounds  are  issued  with  the  projectiles  filled  and  fuzed;  the  shell 
rounds  are  issued  filled  but  not  fuzed,  and  contain  an  adapter  with 
booster  charge. 

The  projectiles  average  in  weight;  shrapnel,  16  pounds  fuzed; 
shell  12.3  pounds  fuzed.  The  components  of  one  round  are  the 
cartridge  case  with  primer,  powder  charge,  projectile,  and  fuze  in 
shrapnel,  and  adapter  and  booster  in  shell. 

75-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1917   (BRITISH). 

The  battery  of  British  75-millimeter  gun  carriages  is  accompanied 
by  the  following  vehicles: 

75-millimeter  gun  carriage  limber,  model  of  1917  (British).1 

75-millimeter  gun  carriage  limber,  model  of  1918.1 

75-millimeter  gun  caisson,  model  of  1918. 

75-millimeter  gun  caisson  limber,  model  of  1918. 

Forge  limber,  model  of  1902  MI. 

Store  limber,  model  of  1902  MI. 

Battery  and  store  wagon,  model  of  1917. 

Battery  reel,  model  of  1917. 

This  gun  was  formerly  3.3  inches  in  caliber  but  was  modified  to 
75  millimeters,  giving  interchangeability  with  French  ammunition. 
All  of  this  materiel  used  by  the  American  Army  was  manufactured 
in  the  United  States.  The  gun  carriage  limber,  model  of  1917,  is  of 
British  design. 

1  Either  one  of  the  above  limbers  may  be  used. 


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75-MILLIMETER  GUN  CARRIAGE  LIMBER,  MODEL  OF  1917 

(BRITISH). 


The  standard  British  limber  carries  cartridges  horizontally,  but 
is  not  arranged  with  compartments  or  diaphragms.  The  American 
product  of  the  British  limber  is  superior  to  the  standard  British 
vehicle  in  that  diaphragms  are  included  in  the  ammunition  chests. 
The  limbers  are  fitted  with  wooden  poles,  which  are  more  liable 
to  breakage  than  steel  poles;  they  have  single  draft  hooks,  in- 
stead of  double  trees  for  equalizing  the  pull  on  the  braces ;  the  pin- 
tle latch  is  not  so  effective  as  the  American,  nor  the  ammunition  chest 
doors  so  well  suited  to  their  purpose;  and  they  are  not  adapted  to 
the  American  harness,  as  the  distance  from  the  neck  yoke  to  the 
draft  hook  is  6  inches  shorter  than  in  the  American  design  and  our 
harness  can  not  be  so  readily  connected  to  the  neck  yoke. 


FRONT   VIEW   OF   LIMBER. 

Weights,  dimensions,  etc. 

Weight,  complete,  empty pounds 1,016 

Weight  of  tools  and  equipment  carried do 114 

Weight  of  ammunition  carried do 516 

Weight,  completely  equipped  and  loaded do 1,  646 

Weight  of  gun,  carriage  and  limber,  completely  equipped  with  21  rounds 

of  ammunition pounds 4,  591 

Diameter  of  wheels inches,-  56 

Width  of  track do 60 

Turning  angle  with  carriage degrees--  70 

The  British  design  of  gun  carriage  limber  is  constructed  of  a  frame 
consisting  of  two  middle  and  two  outer  rails  connected  at  the  front 
and  center  by  a  bar  and  braces  and  surmounted  by  an  ammunition 
chest  of  steel. 

(116) 


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The  chest  opens  at  the  rear  and  is  fitted  with  perforated  diaphragms 
for  carrying  24  rounds  of  fixed  ammunition  and  a  compartment  in 
the  center  holding  two  wooden  trays  for  small  stores. 

The  pole  is  of  wood,  protected  at  the  front  end  by  steel  wrapping 
plates  and  fitted  with  a  neck  yoke  for  use  with  breast  collar  harness. 


REAR  VIEW  OF  LIMBER. 

The  axle  is  a  seamless  steel  tube  fixed  to  the  rails  by  flanges,  and 
the  wheels  are  the  same  as  those  used  on  the  gun  carriage. 

This  limber  is  used  only  in  connection  with  the  75-millimeter  gun 
carriage,  model  of  1917  (British). 

The  75-millimeter  gun  carriage  limber,  model  of  1918  (American) 
a  description  of  which  may  be  found  on  page  119,  can  be  used  as  an 
alternate  for  this  vehicle. 


75-MILLIMETER  GUN  CARRIAGE  LIMBER,  MODEL  OF  1918. 


The  limber  is  of  American  design,  and  is  of  metal  throughout, 
excepting  the  spokes  and  felloes  of  the  wheels.  The  frame  consists 
of  a  middle  rail  and  two  side  rails.  The  middle  rail  is  in  the  form  of 
a  split  cylinder,  one  half  passing  below  and  the  other  half  above 
the  axle,  uniting  in  front  to  form  a  seat  for  the  pole  and  in  the  rear  to 
form  a  seat  for  the  pintle-bearing  guide.  An  automatic  pole  support, 
described  on  page  169,  is  provided. 

The  ammunition  chest  is  a  rectangular  steel  box,  having  a  door  at 
the  rear  hinged  at  the  bottom,  and  swinging  downward  to  an  approx- 
imately horizontal  position.  Three  perforated  diaphragms  within  the 
chest  support  18  rounds  of  fixed  ammunition  and  3  tubular  oil  cans. 

The  axle  is  of  forged  steel,  made  in  one  piece.  The  standard  56-inch 
wheels  are  used.  (See  page  167.) 

This  limber  is  used  in  connection  with  American,  British,  and 
French  75-millimeter  materiel. 

Weights,  dimensions,  etc. 

Weight  complete,  empty pounds 963 

Weight  of  tools  and  equipment  carried,  oil  cans  filled do 134 

Weight  of  ammunition  carried   (shrapnel) do 365 

Weight  of  fuze  boxes,  loaded do 62 

Weight,  completely  equipped  and  loaded do 1,  524 

Rounds  of  ammunition  carried  in  limber  chest 18 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Free  height  under  limber do 24 

Turning  angle  with  carriage degrees—        78 

(119) 


120 


REAR  VIEW   OF   LIMBER. 


FRONT   VIEW   OF   LIMBER. 


121 


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75-MILLIMETER  GUN  CAISSON,  MODEL  OF  1918. 


The  caisson  consists  of  a  steel  chest  carried  on  wheels  and  axle  by 
means  of  a  spring  support.  This  support  consists  of  helical  springs 
held  by  suitable  axle  and  chest  brackets  at  each  end  of  the  chest. 
The  Belleville  springs  absorb  the  shock  of  rebound. 


FRONT  VIEW   OF   CAISSON. 

The  chest  carries  70  rounds  of  ammunition  arranged  in  5  horizontal 
rows  of  14  each.  Protection  from  small-arms  fire  is  provided  by  the 
front  door,  rear  plate,  and  apron,  which  are  made  of  armor  plate. 
The  chest  provides  seats  for  three  cannoneers,  and  is  equipped  with 
fastenings  for  carrying  a  full  complement  of  tools.  A  rack  is  pro- 
vided at  the  back  of  the  chest  for  carrying  fuze  boxes.  On  the 
front  left  side  of  the  chest  is  fastened  the  fuze  setter. 

The  caisson  is  equipped  with  a  short  pole  and  lunette  combined 
with  a  pole  prop.  On  the  rear  the  standard  pintle  is  provided. 

(123) 


124 

Standard  56- inch  wheels  are  used  and  band  brakes  are  provided. 
(See  page  167.) 


GUN    CAISSON    AND    GUN-CAISSON    LIMBER,    LIMBERED. 

Weights,  dimensions,   etc. 

Weight,  complete,  empty pounds —  1,425 

Weight  of  tools  and  equipment  carried do 62 

Weight  of  ammunition  carried   (shrapnel) do 1,421 

Weight  of  fuze  boxes,  loaded do 124 

Weight,  completely  equipped  and  loaded do 3,  032 

Weight  with  limber  completely  equipped  and  with  106  rounds  of  ammuni- 
tion  pounds 4,961 

Rounds  of  ammunition  carried 70 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Free  height  under  caisson • do 81 

Turning  angle  with  limber degrees 81 


75-MILLIMETER  GUN  CAISSON  LIMBER,  MODEL  OF  1918. 


The  gun  caisson  limber  is  practically  the  same  as  the  gun  carriage 
limber,  model  of  1918,  except  that  the  chest  is  larger  and  carries 
more  ammunition.  Each  diaphragm  is  perforated  with  39  flanged 
holes,  which  accommodate  36  rounds  of  ammunition,  and  three 
tubular  oil  cans. 

This  limber  is  used  in  connection  with  the  American,  British,  and 
French  75-millimeter  materiel. 


FRONT  VIEW   OF   CAISSON   LIMBER. 

Weights,  dimensions,  etc. 

Weight,  complete,  empty pounds 1,003* 

Weight  of  tools  and  equipment  carried  (oil  cans  filled) do 134 

Weight  of  ammunition  carried  (shrapnel) do 730 

Weight  of  fuze  boxes,  loaded do 62 

Weight,  completely  equipped  and  loaded do 1,929 

Rounds  of  ammunition  carried  in  limber  chest 36 

Diameter  of   wheels : inches 56 

Width  of  track do 60 

Free  height  under  limber do 24 

Turning  angle  with  caisson degrees—  81 

(125) 


126 


3-INCH  GUN  MATERIEL,  MODEL  OF  1902. 


When  the  United  States  entered  the  World  War  there  were  on 
hand  approximately  544  3-inch  field  guns,  model  1902,  and  the  neces- 
sary equipment  therefor.  The  3-inch,  model  1902,  materiel  includes 
gun,  carriage,  limber,  caissons,  caisson  limbers,  battery  wagons,  forge 
limbers,  store  wagons,  store  limbers,  combination  battery,  store 
wagons  and  limbers,  battery  reel,  also  reel  and  carts,  as  issued  to  the 
75-millimeter  materiel. 

The  needs  of  the  fighting  army  received  first  attention,  but  a  large 
number  of  troops  in  the  training  areas  and  camps  required  materiel 
for  use  in  their  preliminary  instructions;  thus  154  batteries  of  3-inch, 
model  1902,  materiel  were  distributed  for  training  purposes  in  the 
United  States  which  were  considered  substitutes  for  the  75-millimeter 
materiel. 

The  3-inch  field  gun,  American  model  1902-1904-1905,  is  equipped 
with  a  breechblock  of  the  interrupted-screw  type.  The  breech  mecha- 
nism consists  of  a  handle  pivoted  vertically  to  provide  horizontal 
movement  of  the  handle  to  the  right  to  open  the  breechblock.  In 
opening,  the  mechanism  performs  two  functions:  Revolves  the 
breechblock,  releasing  it  from  the  threads,  and  then  swings  the  block 
open.  At  the  same  time  the  cartridge  case  is  ejected  from  the  gun. 
In  closing,  the  threaded  movement  firmly  seats  the  cartridge  in  the 
powder  chamber,  and  the  threads  withstand  the  backward  thrust 
of  the  powder  gases. 

The  recoil  mechanism  is  of  the  hydro-spring  type,  with  the  housing 
attached  to  the  carriage,  and  located  underneath  the  cannon.  The 
firing  mechanism,  in  the  latest  design,  is  operated  either  by  a  lanyard 
attached  to  the  trigger,  or  by  means  of  a  firing  handle  on  the  cradle, 
and  is  of  the  continuous-pull  type.  When  the  breechblock  is  unlocked 
the  gun  can  not  be  fired. 

Weights,  dimensions,  and  ballistics. 
Weight  of  gun : 

Models  of  1902  and  1904 pounds—  835 

Model  of  1905 do 788 

Caliber inches__  3 

Length  of  gun do 87.  8 

Length  of  bore do 84 

Length  of  rifled  portion  of  bore do 72.  72 

55160—21 9  (127) 


128 


FRONT   VIEW   OF   CARRIAGE. 


REAR  VIEW   OF   CARRIAGE. 


(129) 


130 

Rifling : 

Number  of  grooves 24 

Width  of  grooves inch__  0.  2927 

Depth  of  grooves do 0. 03 

Width  of  lands do 0.  01 

Twist,  right-hand : 

Models  of  1902  and  1904 ;  1  turn  in  50  calibers  at  origin  to  1  turn  in 

25  calibers  at  12.52  inches  from  muzzle,  thence  uniform. 
Model  of  1902 :  0  turn  at  origin  to  1  turn  in  25  calibers  at  9.72  inches 
from  muzzle,  thence  uniform. 

\Veight  of  projectile  (filled  and  fuzed) pounds 15 

WTeight  of  cartridge  case_. do 2.  2.~i 

Weight   of   fix^d   ammunition    (1   round) do is.  ir, 

Capacity  of  cartridge  case cubic  inches—  66.  5 

Muzzle  velocity feet  per  sec__  1,  700 

Maximum  pressure  per  square  inch pounds__  33,000 

Range  at  15°  elevation yards__  6,000 

Maximum  range  (approximately) do 8,500 

Weight  of  carriage,  with  4  rounds  of  ammunition  weighing  75  pounds, 

pounds 1,685 

Weight  of  gun  and  carriage,  fully  equipped pound* 2,520 

Weight  at  end  of  trail,  carriage  limbered do 115 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Length  of  recoil  of  gun  on  carriage do 45 

Height  of  axis  of  gun do 40.  875 

Height  of  line  of  peep  sight do 44.  9 

Length  of  peep-sight  radius do 36.  75 

Maximum  angle  of  elevation degrees !•"> 

Maximum  angle  of  depression do 5 

Amount  of  traverse  of  gun  and  carriage 1 mils 140 

Rounds  of  ammunition  carried  on  carriage 4 

3-INCH  GUNS,  MODELS  OF  1902,  1904,  AND  1905,  AND  CARRIAGE, 

MODEL  OF  1902. 

The  guns  are  of  three  models,  1902,  1904,  and  1905,  and  are  prac- 
tically the  same  except  that  the  latter  two  models  differ  from  the 
3902  model  in  breech  mechanism  and  the  1905  model  is  50  pounds 
lighter  in  weight. 

The  gim  is  built  up  of  nickel  steel  and  consists  of  a  tube,  the  rear 
portion  of  which  is  enveloped  by  a  jacket  which  also  projects  beyond 
the  rear  end  forming  a  recess  for  the  breechblock.  A  locking  hoop 
is  shrunk  on  the  tube  and  the  forward  end  of  the  jacket  to  secure 
the  latter  to  the  tube.  The  front  clip  is  a  short  hoop  shrunk  on  the 
tube  near  the  forward  end  which  guides  the  gun  in  recoil. 

The  breechblock  on  all  three  models  is  of  the  interrupted-screw 
type,  and  rotates  in.  the  block  carrier  which  is  hinged  to  the  rear 
end  of  the  tube  on  the  right  side.  The  block  of  the  1902  model  has 
two  threaded  and  two  slotted  sectors  and  the  block  of  the  1904  and 
1905  models,  which  have  identical  breech  mechanisms,  has  four 


(131) 


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133 

threaded  and  four  slotted  sectors.  The  breechblock  is  operated  by 
a  lever  pivoted  to  a  lug  on  the  block  carrier  which  has  at  its  outer 
end  a  handle  and  at  its  pivot  end,  a  segment  of  a  bevel  gear,  meshing 
with  a  corresponding  segment  on  the  rear  face  of  the  block.  On 
pulling  the  handle  to  the  right,  the  first  117°  rotates  the  block  until 
the  threaded  sectors  are  disengaged.  A  further  movement  of  90° 
swings  the  block  and  carrier  on  its  hinge  until  free  of  the  bore. 

The  firing  pin  is  eccentrically  located  in  a  recess  in  the  block, 
when  the  breech  is  open.  As  the  breech  is  closed  the  pin.  is  automat- 
ically moved  to  one  side  until  it  is  in  alignment  with  the  axis  of  the 
bore  and  primer  of  the  cartridge  case.  This  is  a  safety  feature 
which  prevents  the  accidental  discharge  of  a  round  before  the  breech 
has  been  fully  closed. 

The  carriage  is  known  as  model  of  1902.  A  tapering  box-shaped 
trail  is  secured  to  brackets  around  the  axle  and  has  at  its  rear  end  a 
spade  and  float.  Two  compartments  are  provided  in  the  trail,  one 
for  tools  and  one  for  the  rear  sight.  A  seat  is  riveted  to  each  side 
of  the  trail,  one  on  the  left  for  the  gunner,  and  one  on  the  right  for 
a  cannoneer.  In  front  of  the  compartments  are  two  cross  transoms 
which  form  a  support  for  the  elevating  mechanism.  The  cradle  has 
riveted  to  its  underside  a  pintle  which  seats  in  a  pintle  socket  secured 
to  the  axle,  by  means  of  which  the  cradle  and  gun  is  rotated. 

The  top  and  main  shield  and  an  apron  are  provided  for  the  pro- 
tection of  the  personnel  from  gun  fire. 

The  recoil  mechanism  is  of  the  hydrospring  type.  The  recoil 
cylinder  is  fastened  to  the  gun  lug  and  therefore  recoils  with  the  gun. 
The  piston,  rod,  being  secured  to  the  cradle  head,  remains  stationary 
during  recoil. »  Throttling  during  recoil  is  obtained  by  the  use  of 
three  throttling  bars,  on  the  interior  of  the  recoil  cylinder,  the  piston 
having  three  slots  cut  in  it  to  correspond  to  the  throttling  bars. 
During  recoil  the  piston  is  stationary  and  the  hydroline  oil  in  the 
cylinder  is  forced  past  the  piston  through  the  slots.  As  the  throttling 
bars,  due  to  their  increasing  size,  gradually  close  the  slots  in  the 
piston,  the  gun  is  gradually  brought  to  a  stop. 

The  counterrecoil  mechanism  consists  of  three  nests  of  inner  and 
outer  springs  which  function  to  return  the  gun  to  battery  and  serve 
to  partially  check  the  recoil.  The  counterrecoil  buffer  consists  of  a 
tapered  rod  secured  in  the  end  of  the  cylinder  which  enters  the  hollow 
end  of  the  piston  rod,  displacing  the  oil  therein  and  preventing  shock 
when  the  gun  returns  to  battery. 

The  elevating  mechanism  is  of  the  double-screw  type,  consisting  of 
a  screw  pivoted  to  the  rear  end  of  the  rocker,  which  is  moved  up  or 
down  by  the  rotation  of  a  bevel  gear  threaded  on  its  interior  surface. 
This  bevel  gear  is  rotated  by  a  bevel  pinion  operated  by  a  crank 
handle  on  either  side  of  the  trail. 


135 


Traversing  is  accomplished  by  means  of  a  traversing  shaft  oper- 
ated by  a  handwheel  on  the  left  side  of  the  carriage.  This  shaft  is 
threaded  and  passes  through  a  nut  which  is  pivoted  to  the  cradle. 
The  nut  being  secured  to  prevent  its  turning,  swings  the  cradle  in 
traverse,  when  the  traversing  mechanism  is  operated. 

A  lock  is  provided  for  locking  the  cradle  to  the  trail  in  order  to 
relieve  the  elevating  and  traversing  mechanisms  of  any  unnecessary 
strains  during  traveling. 


CARRIAGE    AND    LIMBER   HAULED    BY    TRACTOR. 

Seats  are  supported  on  the  axle  on  each  side  of  carriage  in  front  of 
the  shield  for  the  cannoneers,  when  traveling.  Foot  rests  are  pro- 
vided which  also  support  the  brake  levers  and  ammunition  carriers, 
there  being  four  of  the  latter  which  make  it  possible  to  open  fire 
quickly  if  necessary. 


CARRIAGE  AND   LIMBER  IN   TRAVELING  POSITION. 

The  brakes  are  of  the  shoe  type  and  may  be  operated  from  either 
in  front  or  rear  of  the  shield,  in  the  former  case  when  traveling,  and 
in  the  latter  case  when  in  firing  position. 

Standard  56-inch  wheels  are  used.     (See  page  167.) 

The  instruments  provided  for  sighting  and  laying  the  piece  include 
line  sights,  a  rear  sight,  a  front  sight,  a  panoramic  sight,  and  a  range 
quadrant. 

Three  kinds  of  fixed  ammunition  are  used  in  the  3-inch  gun, 
models  of  1902,  1904,  and  1905,  namely,  common  steel  shell,  common 


136 


137 


138 

shrapnel,  and  high  explosive  shrapnel.  Each  round  is  issued  with 
projectiles  filled  and  fuzed.  The  weight  of  the  projectile  is  15 
pounds  and  the  total  weight  of  one  round  is  18.75  pounds. 

3-INCH  GUN  MATERIEL,  MODEL  OF  1902. 

This  materiel  includes  the  following: 

3-inch  field  gun,  model  of  1902,  1904,  or  1905,  mounted  on  car- 
riage, model  of  1902. 

3-inch  gun  limber,  model  of  1902  and  1916. 

3-inch  gun  caisson,  model  of  1902  and  1916. 

Forge  limber,  model  of  1902  and  1902  Ml. 

Battery  wagon,  model  of  1902,  1902  Ml  and  1917. 

Store  limber,  model  of  1902  and  1902  Ml. 

Store  wagon,  model  of  1902,  1902  Ml  and  1917. 

Battery  reel,  model  of  1917. 

The  above  materiel  is  entirely  of  American  design  and  manu- 
facture. 


3-INCH  GUN  LIMBER,  MODEL  OF  1902. 


The  limber,  excepting  the  spokes  and  felloes  of  the  wheels,  is  of 
metal  throughout.  The  principal  parts  are  the  wheels,  axle,  frame, 
ammunition  chest,  pole,  doubletree,  singletrees,  and  neck  yoke. 

The  wheels  and  wheel  fastenings  are  the  same  as,  and  interchange- 
able with,  those  used  on  the  carriage.  The  axle  is  hollow,  of  a  single 
piece  of  forged  steel,  the  axle  body  being  provided  with  lugs,  to  which 
the  middle  and  side  rails  of  the  frame  are  riveted. 

The  side  rails  are  of  channel  shape,  divided  at  the  front,  one  branch 
being  led  forward  and  secured  to  the  middle  rail  near  the  pole  seat, 


REAR   VIEW   OF   LIMBER. 

while  the  other  branch  is  utilized  as  a  foot-rest  support.  The  foot 
rest  is  a  perforated  steel  plate  formed  to  shape  and  riveted  to  the 
middle  and  side  rails  in  front  of  the  ammunition  chest.  The  rear 
ends  of  the  side  rails  project  slightly  beyond  the  chest  to  form  steps 
for  the  use  of  the  cannoneers  in  mounting. 

The  frame  consists  of  a  middle  and  two  side  rails  riveted  to  the 
axle  lugs.  The  middle  rail  is  in  the  form  of  a  split  cylinder,  one-half 
passing  below  and  the  other  half  above  the  axle,  which  are  joined  in 
front  to  form  a  seat  for  the  pole  and  in  rear  to  form  a  seat  for  the 
pintle  bearing.  The  pintle  bearing  is  of  bronze,  made  in  halves  and 
bored  out  to  take  the  pintle  shank.  The  pintle  has  a  swiveling 
motion  of  360°  upon  its  shank,  but  is  kept  in  its  normal  position  by 
the  spring  in  the  bearing. 

The  doubletrees  and  singletrees  are  formed  of  flange  steel.  Two 
doubletree  rods  each  from  the  ends  of  the  doubletree  to  the  tie-rod 
clamps  on  the  axle  to  which  they  are  pinned.  A  pole  prop  is  hinged 

(139) 


140 

to  the  rear  end  of  the  pole  and  when  not  in  use  it  is  secured  by  fasten- 
ings under  the  limber  frame  and  the  prop-chain  button  on  the  foot  rest. 

The  ammunition  chest  is  a  rectangular  steel  box  built  up  of  sheet 
steel  and  riveted  together.  The  chest  door  is  hinged  at  the  bottom 
and  swings  downward  and  to  the  rear  to  an  approximately  horizontal 
position,  where  it  is  held  by  two  door  chains,  and  is  held  in  its  closed 
position  by  a  shot  bolt  at  each  of  the  upper  corners  and  by  a  lock  in 
the  middle. 

Inside  of  the  chest  the  cartridges  are  supported  by  three  vertical 
diaphragms,  flanged  all  around  and  riveted  to  the  body  of  the  chest. 
Each  of  the  diaphragms  is  perforated  with  39  flanged  holes.  Corre- 
sponding holes  in  the  middle  and  rear  diaphragms  are  connected  by 
conical  brass  tubes,  which  are  cut  away  on  top  to  reduce  weight. 
These  connecting  pieces  support  the  front  end  of  the  cartridge  case 
and  enable  empty  cases  to  be  carried.  The  rear  end  of  the  connecting 
piece  is  turned  over  the  rear  face  of  the  flange  of  the  perforation  in 
the  rear  diaphragm,  and  forms  a  stop  for  the  rim  of  the  cartridge 
case.  The  chest  door  closes  against  the  head  of  the  case  so  that  the 
cartridge  is  firmly  held  in  position.  Suitable  finger  clearances  are 
cut  in  the  flange  of  each  cartridge  hole  in  the  rear  diaphragm  to 
enable  the  fingers  to  get  a  good  hold  on  the  rim  of  the  case  in  with- 
drawing it  from  the  chest. 

Seats  for  three  cannoneers  are  provided  and  the  paulin  issued  with 
each  limber  serves  as  a  seat  cushion.  Watering  buckets  are  carried 
in  suitable  compartments  provided  for  them  between  the  seats  and  the 
chest.  At  each  end  of  the  seat  is  a  handrail  which  projects  above 
the  top  of  the  chest.  At  the  front  a  lantern  and  two  picket 
ropes  are  carried.  Brackets  for  carrying  an  ax,  a  shovel,  and  pole 
prop  are  provided  under  the  limber.  All  of  the  implements  are 
secured  in  their  brackets  by  leather  straps,  and  held  by  strap  fasteners 
provided  for  that  purpose.  With  each  limber  are  issued  three  oil 
cans,  each  of  the  general  form  of  a  cartridge  and  of  a  capacity  of 
approximately  two-thirds  of  a  gallon.  They  are  intended  for  hydro- 
line,  lubricating,  and  coal  oil,  and  are  to  be  carried  inside  the  chest 
in  the  central  vertical  row  of  cartridge  holes. 

Weights,  dimensions,  etc. 

Weight,  complete,  empty —  pounds__  964 

Weight  of  tools  and  equipment  carried do 101 

WTeight  of  ammunition  carried do 675 

Weight,  completely  equipped  and  loaded do 1,  740 

Rounds  of  ammunition  carried  in  limber  chest 36 

Diameter  of  wheels inches —  56 

Width  of  track do 60 

Free  height  under  limber do* 22 

Turning  angle  with  carriage degreos__  80 

Turning  angle  with  caisson do 75 


3-INCH  GUN  CAISSON,  MODEL  OF  1902. 


This  caisson,  with  the  exception  of  the  spokes  and  felloes  of  the 
wheels,  is  of  metal  throughout. 

The  frame  is  diamond-shaped  and  composed  of  two  channel  section 
side  rails  riveted  to  lugs  on  the  axle  and  meeting  in  front  and  rear 
at  the  lunette  and  pintle,  respectively. 


FRONT   VIEW   OF   CAISSON. 

The  ammunition  chest  is  a  rectangular  steel  box  of  flange  steel 
containing  three  vertical  diaphragms  which  support  70  rounds  of 
ammunition.  Caissons  having  serial  numbers  1141  to  1284,  inclusive, 
have  provisions  for  but  56  rounds. 

The  door  of  the  chest  is  in  the  rear  and  hinged  at  the  top,  the  door 
opening  upward  and  held  at  each  end  by  a  prop. 

An  apron  of  armor  plate  is  hinged  under  the  axle  and  may  be 
secured  in  a  horizontal  position  for  traveling. 

A  fuze-setter  bracket  is  pivoted  to  the  apron  hinges  on  the  right 
side  of  the  carriage  at  the  rear.  It  is  raised  and  secured  for  traveling. 

The  road  brake  is  designed  similar  to  that  of  the  gun  carriage,  with 
all  parts  as  far  as  possible  being  interchangeable.  The  standard 
56-inch  wheels  are  used. 

(141) 


142 

Weight,  dimensions,  etc. 

Weight,   empty pounds..  1,  424 

Weight  of  tools  and  equipment  carried do 84 

Weight   of   ammunition   carried do 1,312.5 

Weight,  completely  loaded  and  equipped do 2,820 

Rounds   of   ammunition   carried 70 

Diameter  of  wheels inches 56 

Width    of   track do 60 

Free   height    under    caisson__ do 22.  5 

Turning   angle degrees 75 


3-INCH  GUN  CAISSON,  MODEL  OF  1916. 


The  frame  consists  of  two  side  rails  and  a  middle  rail  braced  by 
tie-rods,  and  by  the  ammunition  chest  to  which  they  are  rivited. 

The  chest  is  a  rectangular  flange  steel  box  containing  three  ver- 
tical diaphragms  supporting  TO  rounds  of  ammunition. 

The  door  is  hinged  to  the  front  of  the  chest,  swings  upward  on 
its  hinges,  and  is  held  by  a  door  prop  on  the  left  side. 

An  apron  of  armor  plate  is  hinged  below  the  chest  for  the  protec- 
tion of  the  personnel. 


FRONT   VIEW.   SHOWING   DOOR    SWUNG    UPWARD    EXPOSING   AMMUNITION. 

Band  brakes  are  used  similar  to  those  on  the  75-mm.  gun  car- 
riage, model  of  1916,  several  parts  of  which  are  interchangeable. 
Brakes  are  applied  by  a  hand  lever  on  the  right  side,  operated  by 
one  of  the  cannoneers  seated  on  the  chest. 

Weights,  dimensions,  etc. 

Overall  length   (traction  pole  removed) inches__  *  64 

Overall  width do *  74 

Overall  height do *  57 

Weight,  empty pounds—  1,  384 

Weight  of  tools  and  equipment  carried do 53.5 

Weight  of  ammunition  carried do 1,312.5 

Weight,  completely  equipped  and  loaded do 2,  750 

Rounds  of  ammunition  carried do 70 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Free  height  under  caisson do 21 

Turning  angle degrees--  81 

•Approximately. 

55160—21 10  ( 1 43  ) 


144 


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145 

3-INCH  GUN  LIMBER,  MODEL  OF  1916. 

With  the  exception  of  the  chest,  the  limber  is  the  same  as  the 
75-millimeter  gun  caisson  limber,  model  of  1918.  The  main  differ- 
ence in  the  chest  is  in  the  size  of  the  holes  in  the  diaphragms,  which 
are  larger  to  accommodate  3-inch  ammunition. 

Weights,  dimensions,  etc. 

Overall   length inches—  *  120 

Overall   width do *  74 

Overall  height do *  63 

Weight,  complete,  empty pounds—  987 

Weight  of  tools  and  equipment  carried  (oil  cans  filled) do 113 

Weight  of  ammunition  carried do 675 

Weight,  completely  equipped  and  loaded do 1,775 

Rounds  of  ammunition  carried  in  limber  chest do 36 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Free  height  under  limber do 24 

Turning  angles  with  carriage degrees 80 

Turning  angle  with  caisson do 81 

•Approximately. 


146 


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51 


BATTERY  WAGON,  MODEL  OF  1902. 


The  frame  consists  of  two  side  rails  joined  at  the  front  to  form  a 
seat  for  the  lunette  bracket  and  projecting  directly  to  the  rear  beyond 
the  axle.  A  forge  vise  is  securely  fastened  to  the  left  side  of  the 
frame  in  place  of  the  handle. 


REAR   VIEW   OF   BATTERY  WAGON. 

The  chest  is  of  wood  and  is  bolted  to  the  side  rails.  The  interior 
is  divided  into  four  compartments;  the  largest  being  accessible 
through  a  hinged  lid  at  either  end  of  the  top.  The  other  three  com- 
partments are  in  the  lower  rear  portion  of  the  chest,  and  are  entered 
by  a  door  at  the  rear  end  which  opens  downward.  Of  the  three 
compartments,  the  right  one  is  for  the  saddler's  chest;  the  left  one 
for  the  carpenter's  chest,  and  the  middle  one  for  the  cleaning  mate- 
rials and  small  stores  chest.  In  the  larger  compartment  is  carried 
the  grindstone  and  frame,  the  jackscrew,  and  the  packing  chest 
containing  spare  breech  mechanism.  A  chest  for  spare  sights  is 
furnished,  which  may  be  carried  either  in  the  battery  or  store  wagon. 

(147) 


148 

In  rear  of  the  axle  and  under  the  chest  are  carried  three  oil  cans 
of  5  gallons  capacity  each. 

Fastenings  are  provided  on  either  side  of  the  chest  for  carrying 
the  two  spare  wheels. 

The  wheels  used  and  carried  are  standard  56-inch.    (See  page  167.) 

This  battery  wagon  is  used  only  in  connection  with  the  3-inch  gun 
materiel,  model  of  1902. 

Weights,  dimensions,  etc. 

Weight  of  battery   wagon,  empty pounds 1, 244 

Weight  of  battery  wagon,  completely  equipped  and  loaded do 2,747 

Diameter  of  wheels inches 56 

Width  of  track do 60 

Free  height  under  wagon do 26 

Turning   angle degrees--         7.1 

BATTERY  WAGON,  MODEL  OF  1902  MI. 

The  battery  wagon,  model  of  1902  MI,  differs  from  the  model  of 
1902  in  the  following  respects: 

The  chest  with  attachments  is  stronger,  better  braced,  and  at- 
tached in  a  better  manner  to  the  frame. 

The  weight  of  the  spare  wheels  is  carried  directly  by  the  axle 
instead  of  at  the  top  of  the  chest. 

The  parts  of  the  chest  are  bolted  and  screwed  together  so  that 
they  may  be  readily  disassembled  if  necessary.  The  corners  are  not 
dovetailed  but  reinforced  with  corner  irons  inside  and  out. 

This  battery  wagon  is  used  only  in  connection  with  the  3-inch  gun 
materiel,  model  of  1902. 

Weights,  dimensions,  etc. 

Weight  of  battery  wagon,  empty pounds 1,  444 

Weight  of  battery  wagon,  completely  equipped  and  loaded do 2,  947 

Diameter  of  wheels inches 56 

Width  of  track do__  60 

Free  height  under  wagon do L'4. ."» 

Turning  angle  with  limber degrees.-        75 

Weight    (approximate)    at  lunette,  loaded pounds 112 


STORE  WAGON,  MODEL  OF  1902. 


The  store  wagon  is  the  same  as  the  battery  wagon,  model  of  1902, 
with  the  exception  that  the  vise  is  omitted  and  a  frame  handle  at- 
tached in  its  place,  and  the  body  has  but  a  single  compartment,  with 
two  doors  on  top.  As  on  the  battery  wagon,  the  store  wagon  carries 
two  spare  wheels  and  three  oil  cans. 


SIDE   VIEW   OF   STORE   WAGON. 

The  store  wagon  is  intended  primarily  for  carrying  such  stores, 
spare  parts,  and  materials  as  can  be  carried  in  the  battery  wagon  and, 
in  addition,  such  stores  as  may  be  designated  by  proper  authority. 

Tire  brakes  are  used,  operated  by  a  hand  lever  on  the  right  side 
of  the  body. 

The  wheels  used  and  carried  are  the  standard  56-inch  wheels.  (See 
page  167.) 

For  detailed  description  and  table  of  weights,  dimensions,  etc., 
see  Battery  Wagon,  page  147. 

(149) 


150 
STORE  WAGON,  MODEL  OF  1902  MI. 

The  store  wagon,  model  of  1902  MI,  is  the  same  as  the  battery 
wagon,  model  of  1902  MI,  with  the  exception  of  the  differences  as 
noted  in  the  description  of  the  battery  store  wagon,  model  of  1902. 

For  detailed  description  and  table  of  weights,  dimensions,  etc.. 
see  page  148. 


151 


FORGE  LIMBER,  MODEL  OF  1902. 


The  frame  of  the  forge  limber  is  identical  in  all  its  parts  with  that 
of  the  3-inch  gun  limber,  model  of  1902.  It  consists  of  a  middle  and 
two  side  rails,  the  middle  rail  being  in  the  form  of  a  split  cylinder, 
one  half  passing  below  and  the  other  half  above  the  axle,  uniting  in 
front  to  form  a  seat  for  the  pole  and  in  the  rear  to  form  a  seat  for 
the  pintle  bearing  guide. 

The  chest  is  a  rectangular  flange-steel  box  having  a  lid  hinged 
along  the  front  edge  of  the  chest  body.  The  lid  is  flanged  all  around, 


TOP  VIEW  SHOWING  INTERIOR  OF  FORGE  LIMBER. 

fitting  over  the  body  of  the  chest  to  make  it  water-tight.     Shot 
bolts  on  the  rear  face  of  the  chest  secure  the  lid  when  closed. 

The  interior  of  the  chest  is  divided  into  five  compartments  by 
four  vertical  steel  partitions.  The  middle  compartment,  which  is 
the  largest,  is  fitted  to  take  the  field  forge,  the  anvil,  and  several 
small  tools,  the  next  compartment  on  either  side  carries  horseshoes 
and  horseshoe  nails,  and  the  end  compartments  are  fitted  with 
fastenings  for  carrying  smiths'  and  machinists'  tools.  A  tubular  oil 

(152) 


153 


JM 


154 

can  is  carried  under  each  end  of  the  chest,  and  various  implements 
are  secured  to  the  chest  by  straps  provided  for  that  purpose. 

Weights,  dimensions,  etc. 

Weight  of  forge  limber,  empty,  without  equipment pounds 958 

Weight  of  forge  limber,  complete  equipped  and  loaded do 1,  577 

Weight  of  store  limber,  empty,  without  equipment do 955 

Weight  of  store  limber,  complete,  equipped  and  loaded do 1, 106 

Diameter  of  wheels inches —        56 

Width  of  track do 60 

Free  height  under  limber do ^6.  5 

Turning  angle  with  battery  wagon degrees—        75 

FORGE  LIMBER,  MODEL  OF  1902  MI. 

The  forge  limber,  model  of  1902  MI,  is  identical  with  the  1902 
model,  with  the  exception  that  the  1902  MI  model  has  an  automatic 
pole  support,  which  is  described  on  page  169. 

The  forge  limber  is  used  in  connection  with  the  American,  British, 
and  French  75-millimeter  materiel,  and  the  3-inch  materiel,  model 
of  1902. 

A  detailed  description  and  table  of  weights  and  dimensions  is  given 
in  a  preceding  article  on  Forge  Limber,  model  of  1902,  page  152. 


STORE  LIMBER,  MODEL  OF  1902. 


The  store  limber  is  practically  the  same  as  the  forge  limber,  model 
of  1902,  except  that  the  chest  is  fitted  with  compartments  for  carry- 
ing fire-control  equipment,  some  of  the  compartments  being  padded 
to  protect  the  contents  from  injury. 

For  description  and  table  of  weights  and  dimensions,  see  preceding 
article  on  Forge  Limber,  model  of  1902. 


TOP    VIEW    SHOWING   INTERIOR    OF    STORE    LIMBER. 

STORE  LIMBER,  MODEL  OF  1902  MI. 

The  store  limber,  model  of  1902  MI,  is  identically  the  same  as  the 
store  limber,  model  of  1902,  with  the  exception  that  it  is  fitted  with 
an  automatic  pole  support,  description  of  which  will  be  found  on 
page  169. 

For  description  and  table  of  weights  and  dimensions,  see  preceding 
article  on  forge  limber,  model  of  1902. 

The  limber  is  used  in  connection  with  the  American,  British,  and 
French  75-millimeter  materiel,  and  the  3-inch  gun  materiel,  model 
of  1902. 

(355) 


BATTERY  AND  STORE  WAGON,  MODEL  OF  1917. 


The  battery  and  store  wagon  is  made  of  metal  throughout,  with 
the  exception  of  the  spokes  and  felloes  of  the  wheels.  The  frame  is 
built  up  of  two  channel  section  side  rails  connected  at  the  rear  and 
intermediate  points  by  similar  channels.  The  side  channels  are  bent 
inward  near  the  front,  meeting  and  forming  a  seat  in  which  the 


REAR  RIGHT   SIDE   VIEW   OF  BATTERY   AND  STORE   WAGON. 

lunette  bracket  is  riveted.     At  the  rear  of  the  frame  is  a  compartment 
for  carrying  recuperator,  lubricating,  and  coal  oil  cans. 

The  chest  is  divided  into  compartments  for  carrying  various  articles 
of  battery  equipment.      The  top  compartments  have  horizontally 

(156) 


157 


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158 

hinged  lids  and  the  lower  compartments  in  front  and  rear  have 
vertical  swing  doors.  Fastenings  are  provided  on  each  side  of  the 
chest  for  carrying  spare  wheels,  and  provision  is  made  for  carrying  a 
spare  limber  pole. 

The  battery  and  store  wagons  are  identical,  except  for  the  tools 
and  accessories  that  are  carried  in  the  compartments  of  each  vehicle. 
A  vise  is  carried  on  the  front  end  of  the  frame  and  a  crowbar  bracket 
on  the  right  side.  The  battery  and  store  wagons  contain  packing 
strips  and  accessories  for  carrying  a  grindstone  in  the  rear  compart- 
ment. 

Standard  56-inch  wheels  are  used.  (See  page  167.)  The  battery 
and  store  wagon  is  used  in  connection  with  the  American,  British, 
and  French  75-millimeter  materiel,  and  with  the  3-inch  gun  materiel, 
model  of  1902. 

Wights,  dimensions,  etc. 

Weight  of  battery  wagon,   empty pounds__  1,  705 

Weight  of  battery  wagon,  completely  equipped  and  loaded do 3.  325 

Weight  of  store  wagon,  empty do 1,  705 

Weight  of  store  wagon,  completely  equipped  and  loaded do 3,  590 

Diameter  of  wheels inches —        56 

Width  of  track do 60 

Free  height  under  wagons do 24.  5 

Turning  angle  with  limbers degrees__        75 

Weight  (approximate)  at  lunette  of  both  wagons,  loaded- pounds__      112 

Overall    length inches—     *132 

Overall  height do *74 

Overall  height do *88 

*  Approximately. 


BATTERY  REEL,  MODEL  OF  1917. 


The  battery  reel,  model  of  1917,  is  a  single  two-wheeled  vehicle 
which  is  drawn  by  4  horses.  It  is  designed  to  carry,  lay,  and  recover 
5  miles  of  insulated  cable,  and  in  addition  carries  2  steel  chests  con- 
taining fire-control  instruments. 

The  frame  is  composed  of  two  side  rails  connected  by  cross  members 
and  diagonal  braces.  Near  the  front,  the  side  rails  converge  and  are 
riveted  to  the  pole  socket.  Axle  brackets  are  riveted  to  the  side  rails, 


LEFT   SIDE   VIEW   OF   BATTERY   REEL. 

in  which  are  mounted  the  axle  arms  for  the  wheels  and  the  drum 
shaft  on  which  the  cable  drum  rotates. 

On  each  side  of  the  drum  are  supports  which  are  joined  across  the 
top  by  a  seat  for  two  men.  Across  the  frame  in  front  of  the  drum  is 
secured  an  instrument  chest  divided  into  two  compartments  with 
separate  hinged  lids,  the  lids  forming  foot  rests  for  the  personnel  on 
the  seat.  Across  the  frame  in  rear  of  the  drum  a  large  steel  chest  is 
supported  on  springs.  It  has  a  lid  hinged  at  the  front  and  provided 
with  guide  rollers  for  the  cable  at  its  rear.  The  larger  fire-control 
instruments  are  carried  in  this  chest  in  specially  designed  com- 
partments. 

55160—21 11  (159) 


160 

On  the  right  side  of  the  drum  is  secured  a  steel  case  in  which  a 
plotting  board  is  carried. 

At  either  end  of  the  drum  is  a  sliding  leather- faced  cone  which  is 
controlled  by  a  hand  lever  at  the  left  end  of  the  operator's  seat. 
When  either  cone  is  engaged,  the  other  is  disengaged.  The  cone  on 
the  left  is  connected  directly  to  a  gear  train  driven  by  a  gear  attached 
to  the  wheel  hub,  and  when  engaged  causes  the  drum  to  revolve. 
As  the  brake  cone  on  the  right  is  engaged  the  clutch  cone  is  thrown 
out  of  engagement.  The  wire,  when  being  laid  out,  leaves  from  the 
top  of  the  drum,  passing  between  the  guide  rollers  attached  to  the 
rear  chest. 

The  cart,  model  of  1918,  together  with  the  reel,  model  of  1909  MI, 
is  issued  in  lieu  of  the  battery  reel,  model  of  1917,  for  motorized 
batteries. 

^eights,  dimensions,  etc. 

Overall  length  (traction  pole  removed) __inches 74 

Overall  width do__  _  73.  7.~i 

Overall  height do__  65 

Weight  of  reel  (without  equipment) __pounds__  1,385 

Weight  of  reel,  completely  equipped  and  loaded do 2,005 

Diameter  of  wheels inches 56 

Width  of  track __do__  60 

Free  height  under  reel do__  19 

Length  of  wire  carried  (approximately) miles 5 


REEL,  MODEL  OF  1909  MI. 


The  reel,  model  of  1909  MI,  is  a  two-wheeled  vehicle  designed  to 
carry,  lay,  and  recover  8  miles  of  insulated  cable.  It  has  interchange- 
able pole  connections  which  enable  it  to  be  adapted  to  either  horse 
or  motor  traction. 

The  frame  is  composed  of  special  shaped  pressed  steel  members 
connected  by  gusset  plates  and  reinforce  pieces,  the  pole  socket  at 
the  front,  automatic  pole  support,  a  pintle  at  the  rear,  and  the  assem- 
bled axle. 


REAR    VIEW    OF   REEL. 

Two  drums  which  carry  the  cable  are  mounted  end  to  end  on  an 
axle  which  rests  in  the  upper  ends  of  the  axle  brackets.  In  order  to 
lay  the  wire,  the  drums  are  disengaged  from  the  clutch,  permitting 
them  to  revolve  free  upon  their  axes,  but  controlled  by  the  braking 
action  of  the  drum  latch  and  drum  brake  or  the  friction  clutch  when 
applied  for  that  purpose.  To  recover  the  cable  or  wind  it  on  the 
drums,  the  clutch  in  the  right  drum  is  applied,  and  the  drum  made  to 
revolve,  by  means  of  the  chain  driving  gear  attached  to  the  right 
wheel.  The  left  drum  is  driven  by  the  right  drum  through  a  pin 
clutch  which  is  operated  by  a  handle  in  the  left  outer  end  of  the  left 
drum. 

(161) 


1(12 


163 


An  operator's  seat  is  secured  to  the  right  rear  corner  of  the  frame, 
and  the  controls  placed  within  easy  reach.  The  clutch  connecting  the 
drum  driving  gear  and  the  right  drum  is  located  in  a  recess  in  the 
right  drum  head  and  operated  by  a  handwheel  at  the  upper  end  of  a 
shaft  mounted  on  the  right  axle  bracket. 

A  lever  on  the  right  side  near  the  seat  operates  the  drum  latch  for 
locking  the  right  drum,  and,  through  the  pin  clutch,  the  left  drum 
when  they  are  at  rest.  A  leather  faced  brake  shoe  attached  to  the 
drum  latch  lever  may  be  brought  against  the  flanged  rim  of  the  right 
drum  end  plate  to  act  as  a  brake. 

A  brake  shoe  controlled  by  a  foot  lever  near  the  operator's  seat  may 
be  brought  to  bear  against  the  flanged  rim  of  the  left  drum  end  plate. 


FRONT   VIEW   OF   REEL. 

Wooden  rollers  are  placed  under  the  frame  so  that  the  wire  will 
be  laid  out  or  recovered  without  injury  to  it. 

A  tool  box  with  lid  opening  on  top  is  secured  to  the  right  of  the 
pole  bracket  in  the  space  between  the  side  rail  and  front  cross  rail. 

The  reel,  model  of  1919  MI.  together  with  the  cart,  model  of  1918. 
is  issued  in  lieu  of  the  battery  reel,  model  of  1917,  for  motorized 
batteries. 

Wcif/hts,  dimensions,  etc. 

Weight  of  reel  (without  load) -__pounds__  1.459 

Weight  of  reel  completely  equipped  and  loaded do 2,426 

Diameter  of  wheels inches 56 

Width  of  track __do 60 

Free  height  under  reel r do 19 

Turning  angle  with  cart degrees 75 

Length  of  wire  carried __yards__  22,  880 


CART,  MODEL  OF  1918. 


The  cart  is  a  two-wheeled  vehicle  made  of  metal  throughout,  with 
the  exception  of  the  spokes  and  felloes  of  the  wheels  and  the  packing 


•  • '.  -   : ' "  ""    • 


VIEW   SHOWING   REEL   AND    CART,    LIMBERED. 

within  the  chest.     It  is  designed  to  carry  part  of  the  fire-control 
equipment  for  the  organization  to  which  it  is  issued. 


REAR   VIEW   OF   CART. 


The  frame  consists  of  a  middle  rail,  two  side  rails,  and  two  axle 
brackets,  all  of  which  support  the  chest.    The  forward  end  of  the 

(164) 


165 


166 

middle  rail  is  fitted  with  a  lunette  and  the  rear  end  with  a  pintle. 
Spiral  springs  are  interposed  between  the  side  rails  and  axle  brackets 
to  absorb  the  shocks  when  traveling.  In  connection  with  the  axle 
brackets,  Belleville  springs  are  used  to  take  up  rebound. 

The  chest  is  made  up  of  flange  steel  plates  riveted  together  and 
fitted  with  doors,  lock  bars,  and  packing  devices,  the  interior  being 
divided  into  17  compartments  of  different  sizes.  The  chest  is  also 
furnished  with  fixtures  on  the  exterior  for  attaching  an  observation 
tower. 

The  road  brakes  are  of  the  contracting  band  type  and  are  operated 
from  the  front  of  the  cart  or  from  the  operator's  seat  on  top  of  the 
chest  by  means  of  a  brake  lever  on  the  right  side. 

This  cart,  together  with  the  reel,  model  of  1909  MI,  is  issued  in  lieu 
of  the  battery  reel,  model  of  1917,  for  motorized  batteries. 

Weights,  dimensions,  etc. 

Overall   length inches--    *  126 

Overall   width do__         *  74 

Overall  height do__         *  62 

Weight,  empty,  without  body  equipment pounds—  1,676 

Weight,  complete  fully  equipped  and  loaded do 2,  004 

Diameter  of  wheels? inches*—        56 

Width  of  track do 60 

Free  height  under  cart  (approximate) do 26 

Turning  angle  with  reel  (approximate) degrees— 

Weight  of  instruments pounds—      431 


*  Approximately. 


THE  56-INCH  WHEEL. 


All  carriages  and  accompanying  vehicles  of  the  3-inch  and  75- 
millimeter  materiel,  of  American  design,  are  equipped  with  standard 
56-inch  wheels,  which  are  interchangeable  for  all  vehicles  of  these 
materiels. 

The  wheel  is  a  modified  form  of  the  Archibald  pattern,  56  inches 
in  diameter,  with  3-inch  tires.  The  tires  are  of  steel.  An  oil  valve 
is  provided  so  that  the  wheel  can  be  oiled  without  removing  it. 


SIDE   VIEW   OF  WHEEL. 

The  wheel  fastening  consists  of  a  bronze  yoke  fitting  in  the  outer 
end  of  the  axle  arm  and  is  accessible  when  the  hub  cap  is  removed. 

THE  57  BY  3.5-INCH  WHEEL. 

In  place  of  the  above  56-inch  wheel  a  57  by  3.5-inch  wheel  may 
be  used. 

It  is  similar  in  design  to  the  56-inch  wheel,  but  is  fitted  with  solid 
rubber  tires. 

Like  the  56-inch  wheel  it  is  interchangeable  on  all  vehicles  of  the 
3-inch  and  75-millimeter  materiel. 

(167) 


REEL,  MODEL  OF  1917,  FOR  CAISSONS. 


One  caisson  in  every  battery  is  provided  with  a  hand  reel  for  tele- 
phone wire.  It  is  riveted  to  the  top  of  the  caisson  and  contains  1 
mile  of  field  wire  so  arranged  that  the  current  goes  through  all  the 
wire.  Terminals  are  provided  for  the  connection  of  the  instruments. 
The  reel  for  caisson,  model  of  1917,  is  a  hand-operated  reel  for  the 
transportation  and  handling  of  telephone  wires. 


REEL,  MODEL  OF   1917,  FOR  CAISSONS,  MOUNTED  ON  A  CAISSON. 

The  frame  is  built  up  of  two  flanged  steel  ends  and  two  sides, 
riveted  together  with  four  angle-iron  corner  reinforces,  and  riveted 
to  the  top  of  the  chest.  The  reel  is  built  up  of  two,  steel,  spool  flanges 
mounted  on  a  shaft,  a  spool  riveted  to  the  right  flange  and  a  basswood 
spool  hub  mounted  between  the  spool  flanges. 

The  spool  may  be  operated  from  either  side.  The  crank  on  the  right 
side  is  mounted  on  the  shaft,  and  when  not  in  use  it  can  be  removed 
and  placed  in  its  provided  receptacle.  The  crank  on  the  left  side  is 
connected  with  the  spool  through  an  18  to  40  gear  reduction.  The 
crank  shaft  is  fitted  with  a  driving  gear  which  meshes  with  a  pinion 
on  the  shaft  of  the  spool.  Chains  are  provided  on  either  end  of  the 
frame  for  locking  the  cranks  when  not  in  use. 

(168) 


169 


The  reel  is  also  fitted  with  a  brake  for  controlling  the  speed  of  rota- 
tion when  allowing  wire  to  run  out.  The  brake  lever  is  pivoted  on 
the  brake-lever  pin,  and  operated  by  a  thong  attached  to  the  lower 


REEL   FOR   CAISSON,   MODEL   OF   1917. 

end  of  the  lever.  By  pulling  the  thong  the  upper  end  of  the  lever  is 
made  to  drag  on  the  inside  of  the  rim  of  the  left  spool  flange.  A 
brake-release  spring,  attached  to  the  upper  end  of  the  lever,  and  a  lug 
on  the  left  shaft  bearing,  keeps  the  brake  open  when  not  in  use. 

THE  AUTOMATIC  POLE  SUPPORT. 

Late  designs  of  limbers  for  75-millimeter  and  3-inch  gun  materiel 
are  fitted  with  an  automatic  pole  support. 

The  pintle  hook  has  a  lug  formed  on  its  lower  side,  which  projects 
backward  and  bears  against  the  lower  side  of  the  lunette  on  the 
drawn  vehicle,  thus  preventing  the  vertical  rotation  of  the  pintle. 


SECTIONAL  DIAGRAM   OF   POLE   SUPPORT. 

The  pintle  bearing  is  pivoted  by  trunnion  bolts  permitting  rota- 
tion in  the  vertical  plane.  A  spring  rod  is  pinned  to  a  lug  on  the  top 
of  this  bearing  and  carries  the  pole  supporting  springs.  This  spring 
is  held  between  a  collar  on  the  rod  and  the  pintle  bearing  guide  so 
that  when  the  weight  of  the  pole  on  the  coupled  vehicle  is  put  on  the 
pintle  it  tends  to  compress  the  spring  until  the  load  is  supported  by  it. 

On  the  pintle  bearing  bolt  is  another  spring,  which  is  compressed 
when  the  pintle  is  drawn  back,  thus  relieving  the  shock  of  starting. 


170 


105-MILLIMETER  HOWITZER  MATERIEL,  MODEL  OF 
1898-09    (GERMAN). 


The  105-millimeter  howitzer  materiel,  model  of  1898-09  (German), 
is  entirely  a  German  product  in  design  and  manufacture.  The  car- 
riage has  several  unique  features  and  differs  in  a  number  of  respects 
from  any  other  carriage  described  in  this  book.  The  cradle  and 
howitzer  are  so  mounted  that  the  breech  of  the  howitzer  is  practi- 
cally at  the  axis  of  elevation.  This  permits  loading  at  any  angle 
of  elevation  without  the  necessity  of  raising  or  lowering  the  piece  in 
order  to  insert  ammunition. 

Because  of  the  opening  in  the  trail,  the  piece  is  permitted  to  recoil 
at  high  angles  of  fire,  and  on  account  of  the  howitzer  being  hinged 
at  the  breech  a  constant  recoil  can  be  maintained  and  the  trunnions 
are  kept  at  a  minimum  height  above  the  ground.  This  location  of 
the  trunnions,  of  course,  necessitates  the  use  of  an  equilibrator  spring 
to  balance  the  overhang  of  the  elevating  parts.  This  is  interposed 
between  the  trail  and  the  cradle. 

This  carriage  seems  to  have  been  very  satisfactory,  as  the  German 
Army  made  very  extensive  use  of  it  during  the  World  War,  mount- 
ing three  different  types  of  guns  on  this  same  type  of  carriage — a 
long  and  a  short  model  of  105-millimeter  field  howitzer  and  a 
77-millimeter  field  gun. 

The  Germans  do  not  appear  to  adhere  to  the  type,  once  it  was 
adopted,  as  firmly  as  did  the  French  to  their  Model  1897.  There 
are  certain  changes  made  in  the  manufacture  of  this  carriage,  and 
no  system  seems  to  have  been  followed  in  applying  them.  To 
illustrate,  there  are  two  distinct  types  of  shields,  three  different 
types  of  cradles,  some  of  which  are  provided  with  an  elevation 
stop,  and  three  types  of  top  carriages.  The  later  type  of  car- 
riage has  a  double  lunette,  the  top  of  which  is  hinged,  and  an  ice 
prong  is  added  to  the  rear  of  the  trail.  These  changes,  however,  do 
not  affect  the  use  of  the  carriage  for  either  of  the  three  types  of  guns 
mentioned. 

The  howitzer  now  in  the  United  States  for  this  carriage  is  known 
as  the  105-millimeter  howitzer,  model  of  1916  (German).  It  has 
a  muzzle  velocity  of  1,402  feet  per  second  and  a  maximum  range 
of  10,930  yards,  the  projectile  weighing  approximately  35  pounds. 
Separate  loading  ammunition  is  used. 

The  recoil  mechanism  used  is  the  hydrospring  type.  It  consists 
of  a  hydraulic-brake  cylinder,  a  spring  return,  and  a  continuous-act- 

(171) 


172 

ing  buffer.  The  length  of  recoil  is  approximately  51  inches  and  is 
constant.  The  maximum  elevation  possible  is  40°,  with  a  10°  depres- 
sion. A  slight  traverse  is  permitted — a  total  of  4°. 

The  battery  equipment  of  each  howitzer  carriage  consists  of  the 
following : 

105-millimeter  howitzer,  model  of  1916  (German). 

105-        "  carriage,  model  of  1898-09  (German). 

105-  howitzer  caisson,  model  of  1898  (German). 

105-        "  howitzer  carriage  and  caisson  limber,  model  of 

1898  (German). 


VIEW   SHOWING   CARRIAGE    LIMBER  AND   CAISSON,    COUPLED. 

Weights,  dimensions,  ballistics,  etc. 

Weight  of  howitzer  with  breech  mechanism pounds 985 

Weight  of  breech   mechanism do 70 

Weight  of  carriage  only do 2,270 

Weight  of  howitzer  and  carriage  in   firing  position do 2,950 

Total    length   of   howitzer inches__  90.9375 

Length  of  tube do 82. 125 

Length  of  tube calibers—  19.  87 

Number  of  rifling  grooves 32 

Diameter  of  wheels inches__  48 

Width   of  tire do 3.  25 

Weight  of  wheel pounds 190 

Track  gauge inches 61 

Height  of  axis  of  gun   above  ground do 41 

Height    of   trunnions    above    ground do 34 

Road    clearance do 16 

Over-all  length,  muzzle  to  center  line  of  lunette do 189.  25 

Elevation,  total degrees—  Minus  10  to  plus  40 

Traverse,  total degrees 4  (71.10  mils.) 


105-MILLIMETER  HOWITZER  AND  CARRIAGE,  MODEL  OF 
1898-09  (GERMAN). 


The  howitzer  consists  of  three  pieces,  a  tube,  a  jacket,  and  a  clip 
hoop.  The  tube  is  the  foundation  of  the  howitzer  and  in  it  is  formed 
the  powder  chamber.  The  breech  end  of  the  tube  is  reinforced  by  the 
jacket,  on  the  bottom  of  which  at  each  end  clips  are  formed  integral 
with  it.  The  clip  hoop  is  forced  on  the  tube  near  the  center  of  its 
length  and  provides  the  forward  clip. 


FRONT  VIEW.   SHOWING   BRAKES  AND   TRAVELING   LOCK. 

The  breech  block  is  the  sliding  wedge-block  type  and  is  operated  by 
a  lever  placed  on  the  upper  right  side  of  the  breech  and  operated  in 
a  horizontal  plane.  The  firing  mechanism  is  the  continuous-pull  type, 
the  mechanism  being  both  cocked  and  fired  by  one  pull  of  the  lanyard. 

The  recoil  cylinder  recoils  with  the  howitzer.  It  is  held  thereto  by 
the  howitzer  retaining  nut.  This  nut  is  locked  in  position  by  a 

(173) 


174 


Illllllll 

QU.(oc8t(j 


175 

locking  plug.  The  rear  end  of  the  cylinder  is  sealed  by  the  rear 
cylinder  head  and  a  copper  gasket.  The  head  contains  the  filling  plug 
and  is  locked  to  the  cylinder  by  a  headless  set  screw.  Twelve  throt- 
tling grooves  of  varying  depth  are  cut  lengthwise  in  the  interior 
surface  of  the  cylinder  wall. 

The  front  end  of  the  piston  rod  screws  into  the  cradle  cap,  so  that 
during  recoil  the  piston  and  rod  remain  stationary  while  the  cylinder 
moves  to  the  rear  with  the  gun.  The  piston  rod  is  hollow  to  within 
a  few  inches  of  the  front  end.  The  buffer,  also  hollow,  is  screwed 
into  the  rear  cylinder  head  and  is  locked  by  a  set  screw.  When 
assembled  in  the  cylinder  the  buffer  fits  inside  the  hollow  piston  rod. 
Two  small  throttling  grooves  are  cut  lengthwise  in  the  buffer.  A 
ball  check  valve  is  located  in  the  rear  end  of  it. 

On  the  front  end  of  the  recoil  cylinder  there  is  a  turned  shoulder 
that  holds  the  front  inner-spring  retainer  in  position  when  the  springs 
are  assembled.  The  front  cylinder  head  is  screwed  in  position  against 
a  copper  gasket  and  is  locked  by  a  leaf  spring.  This  head  forms 
a  stuffing  box  for  the  piston  rod  and  contains  a  bronze  packing  ring, 
leather  and  babbit  metal  packing,  and  the  stuffing  box  nut,  which  is 
locked  to  the  cylinder  head  by  a  leaf  spring. 

The  counter  recoil  mechanism  consists  of  two  spring  columns,  one 
outer  and  one  inner,  of  three  springs  each  placed  end  to  end.  In  re- 
coiling the  cylinder  compresses  the  inner  spring  against  a  rear  spring 
retainer.  This  retainer  gives  the  load  to  a  spring  stirrup  which 
in  turn  gives  the  load  to  an  outer-spring  retainer,  thereby  compressing 
the  outer-spring  column.  The  outer-spring  column  impinges  on 
the  rear  end  of  the  cradle.  The  outer-spring  retainer  has  extensions 
on  each  side  that  move  in  guides  in  the  cradle. 

When  the  piece  is  fired,  the  recoil  cylinder  moving  to  the  rear 
while  the  recoil  piston  remains  stationary,  forces  the  liquid  to  move 
past  the  piston  to  the  rear.  The  only  orifice  for  its  passage,  in 
addition  to  the  slight  clearance  between  the  piston  and  the  cylinder 
wall,  is  through  the  throttling  grooves  cut  in  the  cylinder  wall.  The 
depth  of  the  grooves  is  varied  so  that  the  orifice  area  is  such  that 
the  movement  to  the  rear  is  opposed  by  a  practically  constant  force 
throughout  its  entire  length. 

As  the  recoil  cylinder  moves  to  the  rear  the  buffer  moves  out  of 
the  piston  rod,  creating  a  vacuum  therein  and  causing  the  ball  valve 
to  open,  permitting  some  of  the  liquid,  which  has  passed  the  piston, 
to  flow  into  the  hollow  piston  rod,  so  that  at  the  end  of  recoil  this 
space  is  completely  filled. 

When  the  end  of  the  backward  movement  is  reached,  and  the 
compressed  counterrecoil  springs  act  to  return  the  piece  to  battery, 
the  ball  rolls  to  the  rear,  closing  the  valve  in  the  buffer  rod,  permitting 
the  escape  of  the  liquid  in  the  hollow  piston  rod  only  through  the 

55160—21 T2 


176 

clearance  space  around  the  buffer  and  through  the  two  small  axial 
grooves.  With  the  movement  back  to  battery,  the  liquid  in  the 
rear  of  the  piston  head,  of  course,  returns  past  the  piston  to  the  front 
of  the  cylinder,  but  the  force  of  counterrecoil  stored  in  the  springs 
is  absorbed  mainly  by  the  throttling  of  liquid  in  the  hollow  piston 
rod,  causing  the  piece  to  return  to  battery  without  shock. 

The  cradle  is  constructed  in  the  shape  of  a  tube  of  "  U  "  section 
made  from  sheet  steel  and  having  the  top  covered  by  a  piece  of 
rolled  or  forged  steel  of  such  a  shape  as  to  form  guides  the  full 


EQUILIBRATOR    MECHANISM. 

length  of  the  cradle,  upon  which  the  howitzer  is  supported  and  upon 
which  it  moves  during  recoil.  The  recoil  mechanism  is  contained 
within  the  tube  thus  formed.  The  trunnions  are  riveted  to  the 
cradle  at  the  rear  end  and  two  elevating  segments,  one  on  each  side, 
are  bolted  to  it. 

A  spring  equilibrator  designed  to  counterbalance  the  overhanging 
weight  of  the  tipping  parts  is  interposed  between  the  trail  and  cradle. 
The  spring  column  consists  of  an  inner  and  outer  spring  so  connected 
by  a  stirrup  as  to  work  in  series.  One  end  of  the  column  bears 
against  a  seat  on  the  trail  and  the  other  end  bears  against  a  seat  on 
the  under  side  of  the  cradle,  both  seats  being  of  the  ball  and  socket 


177 

type.  The  force  of  the  spring  very  nearly  balances  the  turning 
moment  of  the,  overhanging  howitzer  and  cradle  whan  at  zero 
elevation,  so  that  very  little  effort  is  required  to  elevate  the  piece. 

The  top  carriage  is  built  up  of  two  side  flasks  of  pressed  steel 
connected  at  the  front  and  rear  by  steel  transoms.  On  the  bottom 
of  the  front  transom  is  a  pintle  which  sets  into  a  pintle  bearing  on 
the  trail.  Riveted  to  the  lower  rear  end  of  each  flask  is  a  clip. 
These  top  carriage  clips  fit  into  two  trail  clips  and  are  supported 
on  small  ball  races  making  traversing  easy.  The  trunnion  bearings 
are  attached  to  the  upper  flanges  of  the  flasks  near  the  rear.  The 
top  carriage  also  carries  the  elevating  mechanism. 


REAR    VIEW    OF    CARRIAGE. 

Elevation  is  accomplished  by  the  double  gear  segments  on  the 
cradle,  operated  through  a  train  of  gears  by  a  handwheel  on  the  left 
side  of  the  top  carriage.  The  maximum  elevation  is  40° ;  the  max- 
imum depression,  10°. 

Traverse  is  accomplished  by  causing  the  top  carriage  to  rotate 
about  the  pintle.  This  is  done  by  means  of  a  screw  fixed  to  the  top 
carriage  and  a  threaded  handwheel  revolving  in  a  bracket  attached 
to  the  left  side  of  the  trail.  The  traverse  is  2°  each  side  of  the  center. 

The  trail  is  provided  with  a  rock  spade  and  a  soft  earth  spade. 
The  latter  folds  under  the  trail  when  not  in  use.  To  prevent  strain 
on  the  elevating  and  traversing  mechanisms  when  traveling  the 
cradle  is  locked  to  the  trail  by  a  locking  device  pivoting  on  the  trail 
and  engaging  clips  on  the  under  side  of  the  cradle.  Shields  of  armor 
plate  are  provided  for  the  protection  of  the  personnel. 


178 

The  wheels  are  of  wood,  48  inches  in  diameter  and  fitted  with  steel 
tires.  The  carriage  is  equipped  with  a  pair  of  tire  brakes  acting 
directly  on  the  tires  of  the  wheels. 

Sighting  is  accomplished  by  means  of  a  quadrant  .sight.  This  Ger- 
man quadrant  sight  is  similar  in  basij  principle  and  method  of 
operation  to  the  quadrant  sight,  model  of  1918  (Schneider),  the  type 
of  combination  sight  and  quadrant  that  is  standard  equipment  of 
the  heavy  artillery.  The  complete  unit  consists  of  a  sight  mount 
and  a  panoramic  telescope,  which  furnishes  the  optiral  element  for 
the  unit.  The  sight  is  of  the  dependent-line-of-sight  type.  It  is 
attached  to  the  left  trunnion  of  the  cradle  on  an  extension  provided 
for  that  purpose. 

Separate-loading  ammunition  is  used  in  this  howitzer.  Only  Ger- 
man ammunition  has  been  issued.  The  shells  are  of  the  high  ex- 
plosive and  illuminating-star-shell  types.  Propelling  charges  con- 
sisting of  flaked  powder  (Wuerfelpulver)  are  made  up  in  bags  and 
enclosed  in  brass  or  steel  cartridge  cases  with  detachable  pasteboard 
or  cork  covers.  Flash  reducers  are  used  for  night  firing.  They 
create  a  dense  smoke  cloud,  thus  masking  the  flame. 

There  are  three  types  of  fuzes,  two  of  which  are  percussion  fuzes, 
and  the  other  is  a  22-second  time  fuze.  The  latter  is  used  on  the 
illuminating  shells. 

105-MILLIMETER  HOWITZER  CAISSON,  MODEL  OF  1898   (GERMAN). 

Weight,  complete,  empty _.-i>ouml$__  1,079 

Weight  of  tools  and  equipment  carried do 

Weight,  completely  equipped  and  loaded do 2, 435 

Rounds  of  ammunition  carried  in  caisson  chest 28 

Diameter  of  wheels inches 53 

Width  of  track __do 61.25 

105-MILLIMETER  CARRIAGE  AND  CAISSON  LIMBER,  MODEL  OF 

1918  (GERMAN). 

Weights,  dimensions,  etc. 

Weight,  empty pounds—       826 

Weight  of  tools  and  equipment  carried do 

Weight  completely  equipped  and  loaded do 2,  035 

Rounds  of  ammunition  carried  in  limber  chest 26 

Weight  at  end  of  pole  fully  equipped  and  loaded- 
Diameter  of  wheels inches__        53 

Width  of  track do 61.25 

Length,  center  of  pintle  to  center  of  wheel do 31.  75 


179 


FRONT     AND     REAR      VIEWS     OF     105-MILLIMETER     CARRIAGE 
CAISSON    LIMBER.     MODEL    OF     1898     (GERMAN). 


180 


FRONT   AND   REAR   VIEW   OF    105-MILLIMETER   HOWITZER    CAIS- 
SON.   MODEL    OF    1898    (GERMAN). 


4.7-INCH  GUN  MATERIEL,  MODEL  OF  1906. 


The  4.7-inch,  model  of  1906,  is  a  mobile  field  gun,  designed  to  fire 
shrapnel  or  shell  at  greater  ranges  than  the  75-millimeter  guns.  In 
order  to  increase  the  range,  a  45-pound  shell  is  provided  to  replace 
the  old  type  60-pound  shell.  The  former  projectile  gives  consider- 
ably higher  muzzle  velocity  and  longer  range  than  the  60-pound  pro- 
jectile. The  life  of  the  gun  before  relining  is  approximately  5,000 
rounds. 

Using  the  60-pound  shrapnel,  a  muzzle  velocity  of  1,700  foot- 
seconds  is  obtained,  with  a  maximum  range  of  7,550  yards  (6,903 
meters)  at  an  elevation  of  15°.  With  the  45-pound  shell,  a  muzzle 
velocity  of  2,050  foot-seconds,  and  a  maximum  range  of  8,700  yards 
(7,900  meters)  is  obtained  at  an  elevation  of  15°,  under  normal 
conditions. 


VIEW   SHOWING   CARRIAGE   AND    LIMBER   IN    TRAVELING    POSITION. 

The  4.7-inch  field  gun  is  mounted  on  a  carriage  of  the  long-recoil 
type,  in  which  the  gun  is  permitted  a  sufficient  length  of  recoil  on  the 
carriage  to  render  the  latter  practically  stationary  under  firing 
stresses.  The  gun,  in  recoil,  is  controlled  by  two  spring  cylinders, 
and  a  hydraulic  cylinder,  which  is  filled  with  25^  pints  of  oil.  In 
recoil,  the  oil  in  the  hydraulic  cylinder  is  forced  from  one  side  of  the 
piston  to  the  other  through  small  portholes.  The  area  of  these  ports 
are  calculated  to  make  the  resistance  which  the  liquid  offers,  plus  the 
resistance  of  the  springs,  such  that  the  wheels  will  not  jump  from 
the  ground  when  the  gun  recoils.  In  counterrecoil  the  oil  is  forced 
back  through  these  small  ports  with  the  result  that  the  return  of  the 
gun  into  battery  is  so  eased  and  regulated  that  shock  and  consequent 
derangement  of  the  aim  is  almost  eliminated.  To  properly  return 
the  gun  to  battery  at  high  angles  of  elevation,  the  springs  are  assem- 
bled with  an  initial  compression  of  approximately  1,500  pounds  in 
each  cylinder. 

(181) 


182 


183 


184 

The  carriage  is  equipped  with  a  single  trail,  composed  of  two  pressed 
steel  flasks,  and  is  anchored  in  the  ground  by  a  spade  when  in  action. 
When  traveling,  the  trail  is  supported  by  the  carriage  limber,  which 
may  be  drawn  by  either  a  truck  or  tractor.  On  account  of  the  single 
trail  the  maximum  elevation  of  the  gun,  without  digging  in  the  trail, 
is  only  15°.  The  allowable  transverse  movement  is  140  mils,  or 
about  8°. 

The  motorized  equipment  of  each  gun  carriage,  as  indicated  below, 
consists  of  a  carriage  limber,  which  supports  the  trail  when  traveling, 
and  three  caissons,  which  carry  ammunition. 

4.7-inch  gun  and  carriage,  model  of  1906. 
4.7-inch  gun  carriage  limber,  model  of  1905. 
4.7-inch  gun  caisson,  model  of  1916  or  1917. 
The  above  materiel  is  entirely  of  American  design  and  manufacture. 


LEFT  FRONT  VIEW  OF  CARRIAGE  EQUIPPED   WITH  BAND  BRAKES. 

Weights,  dimensions,  and  ballistics. 

Weight  of  gun pounds—  2.688 

Total   length inches—      134.  927 

Rifling — Right  hand,  1  turn  in  50  calibers  at  origin  to  1  turn  in  25 
calibers  at  14.9  inches  from  muzzle,  thence  uniform. 

Weight  of  projectile,  base  fuzed  shell  and  shrapnel pounds 60 

Weight  of  point  fuzed  shell do__  45 

Weight  of  powder  charge ounces 95 

Weight  of  cartridge  case pounds — 

Muzzle  velocity  (60  pound  shell  and  shrapnel) ft.  per  sec —  1,  700 

Muzzle  velocity   (45  pound  shell) do 2,050 

Maximum  range  at  15°  elevation  of  45-pound  shell yards —  8,  700 

Maximum  range  at  15°  elevation  of  60-pound  shrapnel do 7,  550 

Weight  of  carriage,  complete  (without  gun) pounds —  5,320 

Weight  of  gun  and  carriage,  fully  equipped do 8,  069 

Diameter  of  wheels inches—  61 

Width   of  wheels do 6 

Height  of  axis  of  gun do 51.  59 

Maximum  angle  of  elevation  (gun  or  carriage) degrees--  15 

Maximum  angle  of  depression  (gun  or  carriage) do 5 

Amount   of  traverse mils —  140(7.8°) 

Height  of  line  of  sight inches—  53.  92 


185 


186 

4.7-INCH  GUN  AND  CARRIAGE,  MODEL  OF  1906. 

TJie  gun  is  of  the  built-up  type,  and  consists  of  a  tube,  jacket,  lock- 
ing hoop,  and  clip.  The  jacket  covers  the  rear  half  of  the  tube,  and 
projects  beyond  the  tube  at  the  rear  to  form  the  breech  recess.  The 


FRONT  VIEW   OF  CARRIAGE   EQUIPPED  WITH   TIRE   BRAKES. 

jacket  is  equipped  with  a  recoil  lug  on  the  underside  for  connecting 
the  recoil  cylinder.  The  clip  is  a  short  hoop  near  the  muzzle  and  is 
fitted  with  guides  to  guide  the  gun  in  the  cradle  on  recoil. 


BREECH  MECHANISM. 


The  breechblock  is  of  the  interrupted  screw  type,  having  four 
threaded  and  four  plain  sectors.  It  is  operated  by  a  handle  which 
swings  from  left  to  right,  turning  and  withdrawing  the  breech  with 
one  motion.  An  extractor  is  fitted  for  throwing  out  the  shell  case 
when  the  breech  is  opened  after  firing. 


187 

The  firing  mechanism  is  of  the  type  known  as  a  continuous-pull 
mechanism ;  that  is,  the  mechanism  is  cocked  and  fired  by  the  pull  on 
the  lanyard  or  by  downward  pressure  on  the  firing  handle  located  at 
the  left  side  of  the  breech. 

The  carriage  is  composed  of  the  following  principal  parts :  Wheels, 
axle,  the  cradle  (for  housing  and  supporting  the  recoil  mechanism 
of  the  gun),  trail,  traversing  and  elevating  mechanisms. 

The  gun  carriage  is  of  the  long-recoil  type,  in  which  the  gun  is 
permitted  to  recoil  on  the  carriage  to  render  the  latter  stationary 
under  firing  stresses.  The  recoil  mechanism  consists  of  an  hydraulic 
cylinder  filled  with  oil,  placed  parallel  to  the  gun,  and  attached  to 
the  cradle.  The  recoil  cylinder  controls  the  backward  movement 
of  the  gun  upon  discharge,  and  the  springs  function  to  return  the 
piece  to  battery  position. 


FIRING  MECHANISM. 

The  recoil  and  counterrecoil  mechanism  is  of  the  hydrospring  type, 
and  consists  of  two  parallel  steel  tubes  (the  spring  cylinders)  fitted 
into  a  frame  and  surrounded  by  rails  which  form  the  gun  slides  and 
the  cradle.  The  recoil  cylinder  is  fitted  between  these  two. 

The  piston  and  spring  rods  are  secured  to  the  gun  lug  and  recoil 
with  the  gun,  while  the  spring  cylinders  and  recoil  cylinder  remain 
stationary. 

The  recoil  is  of  the  constant  type,  being  70  inches  when  the  gun  is 
fired  at  zero  elevation,  and  is  somewhat  greater  at  higher  angles,  due 
to  the  action  of  gravity  on  the  recoiling  parts.  The  recoil  cylinder 
uses  hydroline  oil  as  the  buffer  medium.  Throttling  is  obtained  by 
three  throttling  bars  running  lengthwise  of  the  cylinder,  which  are 
of  varying  height  to  give  a  throttling  effect  with  corresponding  slots 
in  the  recoil  piston.  A  counterrecoil  buffer  is  fitted  in  the  piston  rod 
to  take  up  the  shock  when  the  springs  return  the  gun  to  battery. 


188 


189 

The  trunnions  on  the  cradle  are  mounted  in  bearings  formed  by  a 
yoke  which  swivels  in  a  pintle  bearing  provided  at  the  front  of  the 
trail. 

Traverse  is  obtained  by  means  of  a  handwheel  and  screw  mounted 
on  the  left  side  of  the  trail,  which  swings  the  yoke,  it  carrying  the 
gun  with  it.  A  traverse  of  70  mils  on  each  side  of  center  is  possible. 

The  piece  is  elevated  by  a  double  screw  type  of  mechanism.  The 
upper  end  is  attached  to  the  cradle  and  so  raises  and  lowers  it. 
The  screw  is  operated  through  gearing  by  two  handwheels,  one  on 


FRONT  VIEW  OF  CARRIAGE  EQUIPPED   WITH  BAND  BRAKES. 

each  side  of  the  trail.     From  5  degrees  depression  to  15  degrees 
elevation  is  obtained. 

The  trail  is  of  the  solid  type,  made  up  of  flasks  of  channel  section. 
It  houses  the  axle  and  carries  the  pintle  bearing  in  which  the  top 
carriage,  or  yoke,  swings.  A  tool  box  is  fitted  in  the  trail,  and  a 
seat  is  provided  on  each  side  of  the  trail  for  the  cannoneers.  The 
lunette  transom  is  fitted  about  27  inches  from  the  rear  of  the  trail, 
and  carries  a  bearing  that  fits  the  limber  pintle.  A  trail  prop  is 
provided  for  supporting  the  trail  when  limbering.  The  spade  can 
be  released  and  folded  up  on  the  trail  when  traveling. 


190 


A  traveling  lock  is  provided  on  the  trail  for  locking  the  gun  when 
traveling.  The  piston  rod  and  spring  rods  must  be  disconnected 
before  the  gun  can  be  drawn  back  far  enough  to  lock. . 


REAR   RIGHT   SIDE   VIEW   OF   CARRIAGE. 


The  wheels  are  61  by  6-inch,  rubber  tired,  and  are  equipped  with 
band  brakes.    Some  of  the  older  type  of  vehicles  have  steel  tires  and 


ELEVATING  AND  TRAVERSING  MECHANISMS. 

are  fitted  with  tire  brakes.  An  armor  plate  shield  is  fitted  to  the 
carriage  for  the  protection  of  the  personnel. 

The  sighting  is  similar  to  the  3-inch  gun,  model  of  1902. 

The  instruments  for  sighting  and  laying  the  piece  include  line 
sights,  a  rear  sight,  a  front  sight,  a  panoramic  sight,  and  a  range  quad- 
rant. 


191 


o 


55160—21 13 


192 

The  line  sight  consists  of  a  conical  point  as  a  front  sight,  and  a 
V-notch  as  a  rear-sight.  These  are  located  on  the  jacket  of  the  gun, 
and  are  useful  for  giving  general  direction  to  the  gun. 

The  rear  and  front  sights  are  used  for  direct  aiming.  The  rear 
sight  is  a  peep  sight  mounted  on  range  scale  shanks  on  left  side 


REAR  VIEW  OF  CARRIAGE  EQUIPPED  WITH  TIRE  BRAKES. 

of  the  cradle.  The  front  sight  consists  of  a  pair  of  cross  wires 
mounted  in  a  ring  about  three  feet  ahead  of  the  rear  sight. 

The  sight  shank  has  a  socket  in  which  the  standard  United  States 
panoramic  sight  may  be  mounted. 

On  the  right  side  of  the  cradle  is  mounted  the  range  quadrant, 
which  has  in  combination  with  it  the  angle  of  sight  mechanism.  For 
indirect  fire  the  gunner  on  the  right  of  the  piece  lays  for  range  with 
this  instrument,  and  the  one  on  the  left  lays  for  direction  only. 


193 


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194 

Fixed  ammunition  is  used  with  this  gun;  shrapnel  and  high  ex- 
plosive shell  being  used.    The  base  fuzed  steel  shell  and  the  shrapnel 


FRONT  VIEW  OF  CARRIAGE   EQUIPPED  WITH   TIRE   BRAKES. 

weigh  60  pounds.     The  point  fuzed  shell  weighs  45  pounds.     Gas 
shells  are  also  issued  and  are  identical  with  the  45-pound  steel  shell. 


4.7-INCH  GUN  CARRIAGE  LIMBER,  MODEL  OF  1905. 


The  limber,  a  two-wheeled  vehicle  to  which  the  trail  of  the  car- 
riage is  fastened,  forms  with  the  gun  carriage,  a  four-wheeled  car- 
riage for  the  gun  when  traveling. 

The  carriage  limber  is  designed  to  be  used  with  the  connecting 
pole  for  attachment  to  a  tractor  and  to  support  the  trail  in  traveling. 
The  limber  is  made  of  metal  throughout,  wood  being  used  only  in 
the  spokes  and  felloes  of  the  wheels.  The  principal  parts  are  the 
wheels,  axle,  frame,  top  carriage,  pole  socket,  and  connecting  pole. 

The  top  carriage  is  a  steel  casting,  formed  to  accommodate  the  trail 
of  the  4.7-inch  gun  carriage,  the  trail  resting  on  it  when  en  route. 


FRONT   VIEW   OF   LIMBER. 

The  front  end  of  the  top  carriage  is  provided  with  three  rollers  which 
rest,  and  run  on,  the  top  carriage  rail ;  the  rail  edge  being  equipped 
with  clips  to  prevent  accidental  dismounting.  A  spur  located  on  the 
top  carriage  which  enters  the  trail  holds  the  trail  and  top  carriage  in 
line. 

The  wheels  are  51  inches  in  diameter,  4  inches  wide,  and  are  rubber 
tired.  The  hubs  are  similar  and  interchangeable  with  those  on  the 
wheels  of  the  carriage.  The  axle  is  hollow  and  is  made  from  a  single 
piece  of  forged  steel. 

A  bucket  holder  with  straps  is  located  on  each  side  brace  for  car- 
rying four  canvas  watering  buckets. 

(195) 


19(5 


197 

The  doubletree,  singletrees,  and  pole  complete  are  omitted  for 
motorized  batteries  and  a  connecting  pole  is  used  in  their  place. 
The  standard  short  pole  with  lunette  is  fitted  for  motor  traction,  and 
for  horse-drawn  equipment  the  longer  pole  may  be  substituted. 

Weights  and  dimensions. 

Weight,  complete,  including  spare  connecting  pole pounds—  1,  750 

Weight  of  limber  with  gun  and  carriage,  traveling  position do 9,  818 

Diameter   of  wheels    (rubber   tired) inches 51 

Width    of    track do 60 

Free  height  under  limber  and  carriage do 16.  8 


4.7-INCH  GUN  CAISSON,  MODEL  OF  1908. 


The  4.7-inch  gun  caisson  is  constructed  upon  the  same  general 
plan  as  the  4.7-inch  caisson  limber.  The  wheels,  axles,  pintles  and 
bearings,  lock  bars,  and  most  of  the  implement  fastenings  and  chest 
parts  of  the  two  vehicles  are  exactly  similar  and  interchangeable. 

The  principal  parts  of  the  caisson  are  the  wheels,  axle,  axle  bearings, 
ammunition  chest,  pintle,  connecting-pole  socket,  connecting  pole, 
prop,  apron,  and  brake. 

The  flange-steel  front  plate  and  chest  door  (upper)  of  the  limber 
are,  on  the  caisson,  replaced  by  armor  plates,  for  the  protection  of 


RIGHT   SIDE   VIEW   OF   CAISSON. 

ammunition  servers  from  small  arms  and  shrapnel  fire.  An  apron 
of  armor  plate  is  hinged  to  the  bottom  of  the  caisson  chest  and  extends 
to  within  a  short  distance  of  the  ground  for  the  same  purpose.  This 
apron  swings  forward  against  the  bottom  of  the  ammunition  chest 
to  clear  obstructions  in  traveling,  and  is  held  in  that  position  by 
latches  attached  to  the  sides  of  the  chest. 

The  pole  socket  of  the  caisson  is  made  longer  than  on  the  caisson 
limber,  and  is  fitted  with  rollers  which  serve  as  wheel  guards.  The 
connecting  body  is  made  of  steel  tubing,  its  rear  end  is  finished  to 
fit  the  pole  socket,  and  is  provided  with  a  seat  for  the  rectangular 
key  which  secures  the  connecting  pole  to  the  socket.  A  prop  of 

(198) 


199 

steel  tubing  with  a  bronze  foot  is  attached  to  the  connecting  pole  for 
a  support  when  the  caisson  is  unlimbered ;  when  not  in  use  the  prop 
is  swung  up  under  the  connecting  pole  and  is  held  by  chains. 

The  beams  of  the  road  brake  are  hinged  in  brackets  riveted  to  the 
chest  front.  The  brakes  are  built  up  of  flange  and  forged  steel  parts 
and  carry  cast-iron  shoes  to  bear  against  the  wheel  tires. 

Hangers  for  a  spare  connecting  pole  and  a  bracket  for  a  spare  key 
are  provided  on  the  chest.  The  ax,  hatchet,  lantern,  and  watering 
bucket  fastenings  are  similar,  and  located  like  those  on  the  caisson 
limber.  The  paulin  on  the  caisson  chest  serves  as  a  seat  cushion, 
and  on  either  side  of  the  chest  handrails  provide  handholds  for  the 
cannoneers,  when  mounting  or  dismounting. 

The  opening  between  the  upper  and  lower  intermediate  plates 
on  the  left  side  is  utilized  to  carry  a  two-gallon  oil  can.  Of  every 
four  caissons,  three  carry  oil  cans  containing  lubricating  oil,  and  the 
fourth,  hydroline  oil,  the  contents  of  each  being  indicated  by  a  name 
plate. 

Weights,  dimension,  etc. 

Weight  of  caisson  limber,  empty  (without  implements  or  ammu- 
nition)   pounds—  1,  821 

Weight  of  implements  carried do 85 

Weight  of  ammunition  carried : do 2, 055 

Weight  of  limber,  fully  equipped  and  loaded do 3,  961 

Weight  of  caisson,  empty  (without  implements  or  ammunition) do 2,058 

Weight  of  implements  carried  (including  spare  connecting  pole) do 147 

Weight  of  caisson  fully  equipped  and  loaded do 4,  260 

Rounds  of  ammunition  carried  in  caisson  limber 28 

Rounds  of  ammunition  carried  in  caisson 28 

Diameter  of  wheels . inches 60. 0 

Width  of  track do 60. 0 

Free  height  under  caisson do 19.  55 

Turning  angle degrees 80 


4.7-INCH  GUN  LIMBER,  MODEL  OF  1908. 


The  limber  is  a  two- wheeled  vehicle  provided  with  an  ammunition 
chest  for  the  transportation  of  ammunition  for  the  4.7-inch  gun. 

The  principal  parts  are  the  wheels,  axle,  ammunition  chest,  pintle, 
pole  socket,  pole,  doubletree,  singletrees,  and  neck  yoke. 

The  wheels  and  the  wheel  fastenings  are  the  same  as,  and  are  inter- 
changeable with,  those  on  the  carriage.  The  axle  is  hollow  and  of  a 
single  piece  of  forged  steel.  It  is  secured  to  the  chest  by  axle  bearings 
riveted  to  the  sides  of  the  chest  and  to  the  flanges  of  the  intermediate 
plates. 

The  ammunition  chest  is  built  up  of  flange  steel  and  is  divided 
into  an  upper  and  lower  compartment  by  intermediate  plates.  Cor- 


VIEW   SHOWING   GUN   CAISSON   AND    LIMBER,    LIMBERED. 

responding  holes  in  the  middle  and  rear  diaphragms  are  connected 
by  conical  brass  tubes  called  connecting  pieces,  which  are  cut  away 
on  top  to  save  weight.  These  connecting  pieces  support  the  front  end 
of  the  cartridge  case  and  serve  to  guide  the  projectiles.  The  chest 
doors  close  against  the  heads  of  the  cases  so  that  the  cartridges  are 
firmly  held  in  position.  Suitable  clearances  are  cut  in  the  flange  of 
each  cartridge  pocket  to  enable  the  cartridge  hook  to  get  back  of  the 
rim  of  the  case  in  withdrawing  it  from  the  chest. 

The  doubletree  is  mounted  upon  a  doubletree  pin  projecting  up 
through  a  boss  on  the  forward  end  of  the  pole  socket.  A  limber  prop 
is  hinged  to  the  pole  socket.  When  traveling,  the  prop  is  drawn  up  to 
the  rear  and  held  by  a  chain. 

The  pintle  swivels  360°  in  the  bearing,  but  is  normally  held  in  a 
vertical  position  by  a  spring  bolted  to  the  pintle  bearing  support. 

(200) 


201 

The  right  side  of  this  vehicle  is  equipped  with  fixtures  for  holding  a 
pick,  hatchet,  and  pickax;  while  on  the  left  side  provision  is  made 
for  a  shovel. 

The  paulin  on  the  top  of  the  chest  is  held  in  place  by  straps  suitably 
fastened.  Other  fastenings  on  top  of  the  chest  are  for  a  picket  rope, 
an  ax.  and  a  limber  blanket.  On  the  front  are  attachments  for  a 
wrench  and  a  pole  prop.  The  cartridge  hook  for  use  in  withdrawing 
the  cases  and  projectiles  from  the  chest  is  fastened  on  the  left  side 
of  the  caisson.  A  spanner  for  tightening  the  hub  bands  of  the  wheels 
is  carried  between  the  intermediate  plates. 

The  pole,  doubletree  and  singletrees,  and  neck  yoke  are  standard 
and  interchangeable  with  those  on  any  limber  of  the  battery.  Double- 
tree chains  attached  to  the  chest  body  prevent  excessive  movement  of 
either  end  of  the  doubletree. 

The  4.7-inch  gun  limber,  model  of  1908,  is  only  used  in  connection 
with  the  4.7-inch  gun  caisson,  model  of  1908,  both  being  of  American 
design  and  manufacture.  These  vehicles  are  used  with  motorized  as 
well  as  horse-drawn  batteries  of  4.7  inch  gun  materiel. 


4.7-INCH  GUN  CAISSON,  MODEL  OF  1916. 


The  caisson,  model  of  1916,  is  a  two-wheeled  vehicle  with  an 
armored  ammunition  chest  for  the  transportation  of  ammunition  for 
the  4.7-inch  gun.  This  vehicle  is  designed  to  carry  28  rounds  of 
the  fixed  type  of  ammunition.  The  body  is  suspended  in  such  a 
manner  that  7  rounds  are  carried  below  and  21  above  the  axle. 


RIGHT  FRONT  VIEW  SHOWING  CHEST  DOORS  OPEN,  EXPOSING  DIAPHRAGMS. 

The  chest  is  built  entirely  of  steel,  but  the  upper  door,  rear  plate, 
and  an  apron  hung  under  the  body  are  of  armor  plate  for  protection 
of  the  ammunition  servers  in  the  rear  from  shrapnel  and  small-arms 
fire.  The  doors  open  to  the  front,  and  when  closed  bear  on  the  heads 
of  the  shells.  Suitable  fastenings  are  provided  on  this  chest  for 
carrying  the  usual  complement  of  tools  and  accessories,  also  brackets 

(202) 


203 


204 

for  carrying  fuze  boxes  on  the  outside  of  the  chest.    The  chest  pro- 
vides seats  for  two  cannoneers. 

This  caisson  is  provided  with  an  ammunition  chest  of  sufficient 
size  to  carry  either  shrapnel  or  high-explosive  steel  shells.  It  is  also 
equipped  with  fixtures  for  holding  picks,  shovels,  and  other  tools  on 
the  outside  of  the  ammunition  chest.  By  removing  the  connecting 
pole,  and  adding  double  and  singletrees,  this  vehicle  may  be  trans- 
formed into  a  caisson  limber  suitable  for  horse  traction. 


FRONT   VIEW  OF   GUN  CAISSON. 

The  principal  parts  of  the  vehicle  are  the  wheels,  axle,  ammunition 
chest,  pintle,  brake,  connecting  pole  socket,  and  connecting  pole. 

The  wheels  and  wheel  fastenings  are  the  same  as,  and  are  inter- 
changeable with,  those  on  the  carriage.  The  axle  is  fastened  to  the 
chest  by  axle  bearings  riveted  to  the  chest  sides. 

The  body  of  the  chest  is  of  flange  steel  riveted  together,  forming 
the  top,  bottom,  and  sides  of  the  chest.  The  chest  doors  close  against 
the  heads  of  the  cases  so  that  the  cartridges  are  held  firmly  in  posi- 
tion. Suitable  clearances  are  cut  in  the  flange  of  each  cartridge 


205 

pocket  to  enable  the  cartridge  hook  to  get  back  of  the  rim  of  the  case 
in  withdrawing  it  from  the  chest.  The  chest  doors  open  to  the  front, 
the  lower  door  being  hinged  to  the  bottom  of  the  chest,  the  upper 
to  the  top  of  the  chest,  and  by  means  of  a  lock  bar  the  doors  are 
locked. 

The  armor-plate  apron  is  hinged  to  the  bottom  of  the  caisson,  so 
that  when  traveling  it  may  be  swung  backward  against  the  bottom, 
where  it  is  held  by  latches  on  the  chest  sides. 

The  vehicle  is  equipped  with  a  short  connecting  pole  in  front  pro- 
vided with  a  suitable  prop  for  holding  the  pole  up  when  the  caisson 
is  at  rest.  At  the  rear  is  the  standard  pintle  enabling  other  vehicles 
to  be  connected  en  train. 

On  the  tire  brake  models,  brackets  are  riveted  to  the  end  of  the 
chest.  To  these  brackets  are  pinned  the  brake  beams  by  the  same 
kind  of  leverage  system  as  on  the  carriage.  The  brake  shoes  are 
brought  to  bear  on  the  tire  by  pressure  on  the  brake  lever,  the  brake 
lever  and  segment  being  on  the  left  side  of  the  vehicle. 

The  brake  band  model,  like  the  tire  brake,  has  the  brake  lever  on 
the  left  side  of  the  chest  and  is  of  the  contracting-band-brake  type. 
Pulling  up  on  the  brake  lever  causes  the  brake  bands  to  grip  the 
drums  bolted  to  the  wheels. 

The  top  of  the  chest  has  provision  made  for  carrying  a  picket  rope 
and  spare  connecting  pole,  an  ax,  and  straps  for  holding  a  paulin. 
The  paulin  serves  as  a  seat  cushion.  The  left  side  carries  the  pick, 
mattock,  and  hatchet;  the  right,  a  long-handled  shovel,  cartridge 
hook,  and  pole  socket  key.  On  the  back  are  riveted  a  bucket  holder, 
lantern  bracket,  and  a  foot  rest. 

Between  the  intermediate  plates  in  front  an  oil  can  is  carried  on 
the  right  side,  a  fuze  box  on  the  left,  and  also  a  spanner  wrench.  In 
every  battery  one  caisson  is  provided  with  a  hand  reel  containing 
1  mile  of  wire  as  for  caisson  model  of  1917.  (See  page  168.) 

Weight,   dimensions,   etc. 

Weight  of  caisson,  empty  with  implements  pr  ammunition pounds 2,  565 

Weight  of  implements  carried,  including  spare  constructing  pole do 180 

Weight  of  ammunition do 2,067 

Weight  of  caisson  fully  equipped  and  loaded do 4812 

Round  of  ammunition  carried 28 

Diameter  of  wheels inches 61 

Width  of  track do 60 

Free    height    under    caisson do__        20. 8 


4.7-INCH  GUN  CAISSON,  MODEL  OF  1917. 


The  caisson,  model  of  1917,  is  a  two-wheeled  vehicle  equipped 
with  an  armored  ammunition  chest  for  the  transportation  of  ammuni- 
tion for  the  4.7-inch  gun.  The  two  most  important  changes  from 
previous  models  are:  The  substitution  of  a  band  brake  for  a  tire 
brake,  and  a  spring  support  for  the  ammunition  chest. 

The  principal  parts  of  the  caisson  are :  The  wheels,  axles,  spring 
support,  ammunition  chest,  brake,  pintle,  and  connecting  pole. 

The  wheels  are  60-inch,  steel  tired  with  standard  hubs  and  fasten- 
ers. The  axle  is  a  hollow  single  piece  of  forged  steel.  A  distin- 
guishing feature  of  this  caisson  is  the  spring-supported  chest.  Suit- 
able brackets  are  provided  on  the  chest,  and  arms  on  the  axle  for 
carrying  spiral  springs  to  take  up  road  shocks. 

The  ammunition  chest  is  built  up  of  flanged  steel,  except  the  rear 
plate,  apron  and  chest  doors,  which  are  of  armor  plate.  The  body 
of  the  chest  is  made  of  two  sheets  of  flanged  steel  formed  to  shape 
and  joined  at  the  sides.  Three  vertical  diaphragms  with  connecting 
pieces  provide  an  even  distribution  of  the  load  of  ammunition. 
The  upper  door  when  raised  is  held  at  about  a  60°  angle.  The  lower 
door  is  made  with  an  armor  plate  apron  hinged  to  its  top  edge,  so 
that  when  it  is  dropped,  it  forms,  with  the  upper  door  and  rear  plate, 
an  armor-plate  protection. 

The  road  brake  is  of  the  contracting-band-brake  type  and  is  oper- 
ated from  the  right  side  of  the  chest  by  pulling  up  on  the  brake 
lever;  this  through  a  linkage  causes  the  brake  bands  to  grip  the 
drums  of  the  wheels. 

The  connecting  pole  is  attached  to  the  caisson  by  a  socket,  the 
inside  being  tapered  to  accommodate  the  rear  end  of  the  connecting 
pole,  also  the  horse  pole. 

The  foot  rests  of  commercial  flange  steel  are  riveted  to  the  upper 
chest  door;  these  also  serve  as  handles  in  opening  and  raising  the 
door.  A  lantern  bracket,  and  fastenings  for  holding  a  pick,  shovel, 
lunette,  and  spanner  wrench  are  riveted  to  the  rear  plate.  At  the 
top  are  riveted  fastenings  for  holding  an  ax,  connecting  pole;  also 
strap  fastenings  for  the  paulin  and  the  caisson  blankets.  A  car- 
tridge hook  and  hatchet  fastenings  are  riveted  to  the  left  side  of  the 
chest. 

Of  every  four  caissons  three  carry  lubricating  oil  and  one  hydroline 
oil.  One  caisson  in  every  battery  is  provided  with  a  reel  for  caisson, 

(206) 


207 


55160—21- 


-14 


208 

model  of  1917,  which  is  riveted  to  the  top  of  the  caisson  and  contains 
1  mile  of  field  wire  for  telephoning  purposes.    (See  page  168.) 

By  changing  the  connecting  pole  and  adding  the  doubletree  and 
singletrees  this  caisson  is  converted  into  a  caisson  limber.  A  standard 
pintle  with  a  semiautomatic  latch  is  provided  at  the  rear. 

Weights  and  dimensions. 

Weight  of  caisson,  empty,  without  implements  or  ammunition pounds 2, 053 

Weight  of  implements  carried,  including  spare  pole do 180 

Weight  of  ammunition do 2, 067 

Weight  of  caisson  fully  equipped  and  loaded do 4, 300 

Rounds  of  ammunition  carried 28 

Diameter  of  wheels inches 60 

Width  of  track__  __do__  60 


5-INCH,  60-POUNDER  GUN  MATERIEL  (BRITISH). 


The  United  States  procured  a  number  of  batteries  of  5-inch,  60 
pounder  guns  with  the  necessary  accompanying  vehicles  from  Great 
Britain. 

The  materiel  is  of  British  design  and  manufacture  throughout, 
and  the  units  ceded  to  the  United  States  include  the  gun,  Mark  I, 
mounted  on  a  carriage,  Mark  II ;  the  gun  carriage  limber,  Mark  II, 
the  ammunition  wagon,  Mark  II ;  and  the  ammunition  wagon  limber, 
Mark  II. 

The  materiel  was  originally  designed  for  horse  transportation  and 
thus  is  provided  with  poles  and  the  necessary  attachments  for  horse 


REAR  LEFT  VIEW  OF  CARRIAGE  IN  BATTERY. 

draft.  By  substituting  the  engine-draft  connector  in  place  of  the 
horse- draft  poles,  the  materiel  is  converted  into  motorized  batteries 
and  may  be  drawn  by  tractors.  When  horse  drawn,  it  is  customary 
to  divide  the  four  vehicles  into  two  trains,  each  having  two  vehi- 
cles ;  however,  when  the  battery  is  adapted  for  motor  draft,  the  four 
vehicles  are  drawn  as  one  train. 

The  load  of  the  gun  carriage  and  limber  is  about  as  heavy  as  is 
practicable  for  horse  transportation,  although  the  British  originally 
designed  their  8-inch  howitzer  materiel,  which  is  of  greater  weight, 
for  horse  transportation. 

The  carriage  is  of  the  constant  recoil  type,  the  recoil  mechanism 
being  of  the  hydrospring  type,  located  above  the  gun.  The  recoil 
mechanism  consists  of  two  spring  cylinders  and  one  hydraulic  cylinder 
filled  with  glycerine  and  water. 

The  piston  rod  of  the  recoil  cylinder  and  the  rods  of  the  two  spring 
cylinders  are  connected  to  the  lug  on  the  breech  ring  of  the  gun  and 
therefore  recoil  with  the  gun. 

(209) 


H 


210 


5     x 

I  I 


211 

Upon  recoil  of  the  gun,  the  liquid  is  forced  past  the  piston  head 
through  a  throttling  groove  or  slot  cut  in  the  wall  of  the  cylinder. 
The  resistance  offered  by  the  action  of  the  liquid  in  the  cylinder, 
together  with  the  resistance  offered  by  the  compression  of  the  springs 
in  the  cylinders,  controls  and  absorbs  the  shock  of  recoil,  permitting 
the  carriage  to  remain  practically  stationary  upon  the  ground  when 
the  piece  is  fired. 

The  energy  stored  up  in  the  spring  cylinders  due  to  the  compres- 
sion of  the  springs  during  recoil  is  sufficient  to  cause  the  gun  to  re- 
turn to  the  firing  position. 

A  hydraulic  counterrecoil  buffer  is  provided  at  the  front  of  the 
hydraulic  cylinder  and  acts  as  a  cushion,  thereby  preventing  the 
violent  return  of  the  gun  to  firing  position. 


VIEW    SHOWING   TRAIL   CONNECTED   TO    LIMBER. 

A  range  of  12,280  yards  (11,230  meters)  is  possible,  when  firing  a 
60-pound  projectile  with  a  muzzle  velocity  of  2,080  feet  per  second 
at  the  maximum  elevation  of  21£°. 

The  carriage  is  equipped  with  tractor  wheels  provided  with  inde- 
pendent wheel  brakes. 

The  trail  is  of  the  single  unit  type,  being  broadened  at  the  spade 
end  and  equipped  with  a  fixed  spade  for  anchoring  the  trail  to  the 
ground. 

When  traveling,  the  carriage  is  connected  to  the  limber  by  an 
adjustable  connecter. 

The  carriage  permits  elevation  from  5°  depression  to  21£°  eleva- 
tion. The  carriage  permits  traverse  of  4°  left  and  4°  right,  when  it 
is  elevated  at  16^°  or  less.  At  higher  elevations  the  traverse  is  but 
3°  right  and  3°  left,  due  to  the  interference  of  the  trail  with  the  gun 
at  these  elevations. 


212 

Weights,  dimensions,  and  ballistics. 

Weight  of  carriage  and  gun pounds—  12,  096 

Weight  of  gun  and  breech  mechanism do 4,  858 

Weight  of  carriage do 7, 238 

Weight  of  projectile do GO 

Weight  of  powder  charge do 9.  44 

Pressure  of  trail  on  ground do 920 

Length  of  gun inches 168.  05 

Length,  over  all,  of  carriage  and  limber,  traveling  position,  with  gun  but 

without  limber  pole feet—  28. 625 

Length,  over  all,  of  carriage  and  limber,  traveling  position,  with  gun  and 

pole feet—  37^6 

Length  between  axles,  of  carriage  and  limber,  traveling  position— do 13.  75 

Height  of  axis  of  gun  from  ground inches—  51.  5 

Maximum  elevation degrees—  21. 5 

Maximum  depression _, do 5 

Traverse  (at  elevation  of  16 J°  or  less)  : 

Degrees  right 4 

Degrees  left 4 

Traverse  (at  elevation  above  16^°)  : 

Degrees  right 3 

Degrees  left 3 

Range,  maximum yards 12,  280 

Muzzle  velocity,  normal ft.  per  sec 2, 080 

Rifling,  uniform  1  turn  in  30  calibers. 

Diameter  of  carriage  wheels inches 60 

Track,  center  line  to  center  line  of  wheels do 63.  5 

Diameter  of  turning  circle feet 54 


5-INCH,  60-POUNDER  GUN,  MARK  I,  AND  CARRIAGE, 
MARK  II  (BRITISH). 


The  gun  is  of  the  wire  wound  type  and  consists  of  two  tubes, 
jackets,  breech  bush,  breech  ring,  and  several  layers  of  steel  wire. 
The  inner  tube  extends  the  length  of  the  barrel,  the  outer  tube  being 
shrunk  upon  it,  extending  over  the  rear  of  the  inner  tube  to  form  a 
threaded  bearing  for  the  breech  bush  which  receives  the  breech  block. 
The  jacket  is  fitted  over  the  tubes  and  extends  to  the  rear,  having 
a  threaded  section  on  which  the  breech  ring  is  received.  Several 
layers  of  steel  wire  are  interposed  between  the  jacket  and  tubes, 
the  jacket  being  shrunk  over  the  wire.  The  breech  ring  is  provided 
at  the  top  with  a  lug,  to  whicji  the  recoil  piston  rod  and  the  rods  of 
the  spring  cylinders  are  secured,  being  the  direct  connection  between 
the  gun  and  recoil  mechanism,  and  is  provided  with  lugs  at  the  right 
side  which  accommodate  the  breech  carrier.  On  either  side  of  the 
jacket  longitudinal  projections  are  provided,  which  engage  and  slide 
in  corresponding  slots  in  the  cradle. 

The  breech  block  is  of  the  interrupted  screw  type,  having  threaded 
and  slotted  sectors.  The  breech  bushing  is  threaded  and  recessed 
to  correspond  with  the  sectors  on  the  breech  block.  The  breech 
mechanism  is  so  arranged  that  by  one  pull  of  the  breech  lever  from 
left  to  right  the  breech  screw  is  unlocked  and  the  screw  and  carrier 
swung  into  loading  position.  After  loading,  one  thrust  of  the  same 
lever  inserts  the  breech  screw  into  position  in  the  breech  bush  and 
turns  it  into  the  locked  position. 

The  breech  screw  is  supported  by  the  carrier,  which  pivots  and  is 
hinged  to  the  lugs  provided  on  the  right  side  of  the  breech  ring. 

The  firing  mechanism  is  of  the  "  T  "  type  and  is  fitted  with  a  safety 
device  which  prohibits  the  firing  of  the  gun  until  the  breech  is  closed. 
Discharge  is  by  means  of  a  lanyard  operated  from  the  right  side  of 
the  carriage. 

The  carriage  consists  of  the  following  major  parts :  Cradle,  includ- 
ing recoil  mechanism ;  top  carriage ;  elevating  and  traversing  mech- 
anisms ;  trail ;  brake  gear ;  wheels  and  axle. 

The  carriage  is  constructed  on  the  long  recoil  principle,  having 
practically  a  constant  length  of  recoil  at  all  elevations.  The  length 
of  recoil  is  approximately  57  inches.  The  recoil  mechanism  is  placed 
parallel  with,  and  located  above  the  gun,  the  gun  sliding  during 
recoil  and  counterrecoil  in  slides  provided  in  the  cradle. 

(213) 


214 


The  recoil  mechanism  being  of  the  hydro-spring  type,  utilizes  two 
spring  cylinders  and  one  hydraulic  cylinder,  independent  of  each 
other,  and  held  in  relative  position  by  the  cradle.  The  cradle  is 
cylindrical  in  form  and  inclosed  the  breech  end  of  the  gun,  and  is 
provided  with  threaded  holes  at  the  front  and  rear  for  the  reception 
of  the  spring  and  hydraulic  cylinders,  which  are  screwed  into  these 
holes.  The  three  cylinders  extend  to  the  rear  and  engage  suitable 
holes  in  the  breech  ring  to  which  they  are  fastened  by  connecting 
pieces,  the  two  spring  cylinder  rods  being  retained  by  nuts,  and  the 
hydraulic  cylinder  rod  by  an  externally  threaded  collar  which  passes 
through  the  breech  ring  and  engages  the  thread  on  the  piston  rod, 
the  three  rods  recoiling  to  the  rear  with  the  gun. 

The  trunnions  of  the  cradle  are  received  in  bearings  in  the  top  car- 
riage, which  in  turn  is  pivoted  on  the  front  end  of  the  trail  to  permit 
traverse. 


REAR   RIGHT   VIEW   OF   CARRIAGE. 

Traverse  and  elevation  is  accomplished  through  the  medium  of 
handwheels  located  on  the  left  side  of  the  carriage.  The  elevating 
handwheel  actuates  a  pinion  meshing  with  a  rack  bolted  to  the 
cradle.  The  traversing  handwheel  operates  a  screw,  one  end  of 
which  is  hinged  on  the  top  carriage,  the  other  end  engaging  a  nut 
which  pivots  on  the  trail. 

Traversing  stops  are  provided  on  either  side  of  the  top  carriage 
to  limit  the  traverse  to  4°  right  and  4°  left,  when  the  gun  is  elevated 
at  16£°  or  less. 

The  amount  of  traverse  is  indicated  by  a  pointer  fixed  to  the  trail, 
which  reads  to  a  graduated  scale  on  the  rear  transom  of  the  carriage. 

The  trail  is  of  the  solid  type,  being  cut  out  at  the  front  to  give 
clearance  to  the  breech  of  the  gun  during  recoil,  and  at  high  eleva- 
tions. The  front  end  of  the  trail  is  equipped  with  bronze  brackets 
through  which  the  axle  passes.  The  trail  has  a  bearing  at  the 


215 

forward  section  on  which  the  top  carriage  rests  and  pivots,  and 
through  which  the  pivot  pin  passes,  retaining  the  top  carriage  in 
proper  position.  Clips  are  provided  on  the  trail  which  engage  pro- 
trusions on  the  top  carriage,  preventing  vertical  movement  of  the 
top  carriage  when  the  gun  is  fired.  Traversing  stops  are  provided 
to  prohibit  traversing  of  more  than  3°  left  and  3°  right,  when  the  gun 
is  elevated  above  16£°. 

The  rear  end  of  the  trail  is  equipped  with  a  connector  for  limber- 
ing the  carriage  to  the  carriage  limber.  The  connection  is  held  in 
position  by  pins,  and  is  provided  with  holes  for  adjustment. 

A  spade  of  the  fixed  type  is  riveted  to  the  rear  end,  and  holds  the 
trail  in  a  practically  stationary  position  when  the  gun  is  in  action. 

A  traveling  lock  is  provided  on  the  trail  which  engages  the  breech 
of  the  gun  at  0  degree  elevation,  when  traveling.  The  lock  is  hinged 
to  the  inside  of  the  trail  members  and  swings  down  when  the  gun 
is  in  firing  position. 

The  wheels  are  of  the  tractor  type,  being  provided  with  diagonal 
cleats  riveted  to  the  rims.  The  wheels  are  60  inches  in  diameter 
and  have  tires  12  inches  in  width. 

A  "brake  ring  is  provided  on  each  wheel  against  which  an  internal 
brake  shoe  is  fitted,  which  is  operated  by  a  handwheel  at  the  front 
of  the  carriage. 

Sighting  is  accomplished  by  means  of  a  tangent  sight  and  foresight 
on  the  right  side  of  the  carriage,  and  by  an  oscillating  sight  and  dial 
sight  (panoramic  sight)  on  the  left  side  of  the  carriage. 

The  tangent  and  foresight  together  form  an  open  sight  for  the 
direct  laying  of  the  gun. 

The  oscillating  sight  on  which  the  dial  sight  is  mounted  is  used 
for  indirect  laying;  the  oscillating  sight  being  used  for  laying  in 
elevation  and  the  dial  sight  for  direction. 

Ammunition  of  the  separate  loading  type  is  used,  being  both  ex- 
plosive shell  and  shrapnel.  The  weight  of  each  is  60  pounds.  The 
propelling  charge  consists  of  9  pounds  7  ounces  of  cordite.  Nor- 
mally these  charges  are  not  separate  for  zone  fire,  although  special 
charges  are  sometimes  made  up  for  this  purpose. 


5-INCH,  60-POUNDER,  GUN  CARRIAGE  LIMBER,  MARK  II 

(BRITISH). 


The  limber  consists  mainly  of  a  steel  frame,  two  steel  chests,  wheels, 
axle,  and  draft  connections. 

The  vehicle  is  designed  for  2-horse,  4-horse,  or  tractor  draft.  When 
horse  drawn,  the  front  end  of  the  frame  is  equipped  with  a  wooden 
horse  pole,  which  is  retained  in  place  by  a  pin  passing  vertically 
through  the  rail  and  pole,  and  is  also  equipped  with  two  or  four 
singletrees,  as  the  draft  may  require.  Chains,  with  the  necessary 
draft  connections,  are  also  provided,  and  extend  from  two  points  on 
the  frame  to  the  forward  section  of  the  pole,  thereby  adapting  the 
vehicle  for  additional  horse  draft.  The  necessary  neck  yoke  bars  are 
provided  on  the  draft  pole. 


FRONT   VIEW   OF   CARRIAGE   LIMBER. 

For  4-horse  draft,  the  two  outside  singletrees  are  suspended  from 
outriggers  which  are  hinged  to  the  main  frame,  and  are  steadied  by 
stays  extending  back  to  the  axle  arms. 

For  2-horse  draft,  the  two  outside  singletrees  are  removed,  the 
stays  disconnected,  and  the  outriggers  folded  back  and  over  the  main 
frame,  being  held  in  the  latter  position  by  straps. 

The  singletrees,  when  removed,  are  strapped  across  the  center  of 
the  frame  forward  of  the  steel  chests. 

For  tractor  draft,  all  the  singletrees  are  removed  and  strapped  to 
the  frame,  the  horse  pole  being  removed  and  replaced  by  the  motor 
draft  connector  which  is  pinned  to  the  frame. 

(216) 


217 

The  frame  consists  principally  of  four  side  rails,  two  inner  and 
two  outer,  connected  at  the  rear  to  the  axle  by  flanges  and  pins. 
The  front  end  is  joined  together  by  connecting  plates,  the  frame 
being  strengthened  by  diagonal  stays. 

In  th«  rear  of  the  frame  at  the  center,  a  pintle  is  provided,  which 
accommodates  the  adjustable  connector  on  the  trail  of  the  carriage 
in  traveling  position.  The  pintle  is  provided  with  a  thumb  latch 
which  prevents  accidental  unlimbering  of  the  trial  connector. 

The  steel  chests  are  riveted  to  the  main  frame  at  the  rear,  on  either 
side.  The  inner  rear  corners  of  these  chests  are  formed  diagonally 


REAR   VIEW   OF   CARRIAGE   LIMBER. 


to  allow  clearance  to  the  swing  of  the  connector  on  the  carriage, 
when  traveling. 

The  chests  are  of  flanged  steel,  having  lift  lids  which  are  hinged 
at  the  front  side  and  are  equipped  with  hasps,  locks,  and  chains  at 
the  rear.  The  interior  of  each  chest  is  fitted  for  carrying  stores,  and 
each  is  provided  at  the  top  with  a  tray  which  carries  small  stores. 
The  left  chest  is  constructed  to  carry  the  sights  and  attachments, 
together  with  a  number  of  small  tools,  and  one  powder  charge  in  a 
tin  box.  The  right  chest  carries  the  clinometer,  oil  can,  and  other 
various  tools  and  accessories,  together  with  one  powder  charge  in 
a  tin  box. 

Extending  from  the  base  of  each  chest  toward  the  rear  a  steel 
bracket  is  provided  on  which  one  round  of  ammunition  is  carried. 


218 

The  shell  is  held  in  a  vertical  position  on  this  support  by  a  bronze 
bracket  and  a  strap. 

Suspended  below  the  frame  at  the  rear,  a  wire  net  tray  is  provided 
for  carrying  drag  ropes  and  lashings. 

Forward  of  the  steel  chests,  on  the  top  of  the  frame,  a  board  is 
fastened,  extending  across  the  frame,  and  is  equipped  with  friction 
clips  for  the  accommodation  of  two  rifles. 

The  wheels  provided  are  60  inches  in  diameter,  having  steel  tires 
6  inches  in  width.  The  outer  end  of  the  axle  arms  are  equipped  with 
drag  washers  to  assist  hauling.  No  brakes  are  provided  on  this 
vehicle. 

Weights,  dimensions,  etc. 

Weight  without  two  projectiles 1 pounds 2, 240 

Weight  on  limber  pintle,  traveling  position do 641 

Weight  on  pole,  carriage  limber  (at  center  tug  hole)  : 

Without  two  projectiles do 51 

With  two  projectiles do 39 

Diameter  of  wheels inches 60 

Track  of  wheels,  center  line  to  center  line do 63.  5 

Length : 

With  horse  pole do 186 

Without  horse  pole do 77 

Width : 

Over  axle  with  dust  caps do 78.  5 

Outriggers  extended do 110 

Outriggers  folded do 65 


5-INCH,  60-POUNDER,  AMMUNITION  WAGON,  MARK  II 

(BRITISH). 


The  ammunition  wagon  (caisson)  consists  principally  of  a  steel 
frame,  ammunition  chest,  fuze  lockers,  brake  gear,  draft  fittings, 
wheels,  and  axle. 

The  wagon  is  constructed  to  carry  24  rounds  of  ammunition, 
24  powder  charges  in  tin  containers,  and  2  fuze  boxes.  The  exterior 
is  fitted  with  fastenings  to  carry  ropes,  handspikes,  also  other  tools 
and  accessories. 


FRONT  VIEW  OF  AMMUNITION  WAGON. 

The  ammunition  chest  is  constructed  of  flange  steel,  having  flange 
steel  brackets  on  either  side  at  the  center,  which  extend  below  the 
chest,  providing  bearings  which  receive  the  axle. 

The  interior  of  the  chest  is  divided  into  a  front  section  and  a  rear 
section,  by  a  vertical  steel  plate  passing  through  the  chest  parallel 
to  the  axle.  Each  section  is  divided  by  steel  plates  passing  crosswise 
through  the  chest  into  three  horizontal  rows  of  compartments.  The 
lower  compartments  contain  4  high-explosive  shell  and  4  shrapnel. 
The  middle  row  contains  2  high-explosive  shell,  2  shrapnel,  2  powder 
charges  in  tin  containers,  1  fuze  box  containing  14  fuzes,  and  1  empty 
compartment.  The  upper  row  of  compartments  contain  10  powder 
charges  in  tin  containers. 

(219) 


220 

The  powder  charge  containers,  and  the  shell  are  retained  in  the 
proper  position  by  quick  release  straps,  and  the  shell  are  withdrawn 
from  their  respective  compartments  by  means  of  the  packing  blocks 
which  inclose  the  nose  of  the  shell,  and  by  the  withdrawing  straps 
provided.  The  withdrawing  straps  extend  the  length  of  the  shell 
and  are  fastened  to  the  nose  blocks,  and  are  also  rivited  to  the  com- 
partment plates,  preventing  their  complete  removal.  When  the 
shell  is  withdrawn  about  half  its  length,  the  withdrawing  strap  is 
slipped  over  the  base  of  shell  allowing  the  complete  removal  of  the 


REAR  VIEW   OF  AMMUNITION   WAGON. 

shell,  while  the  packing  blocks  and  straps  are  held  in  their  respective 
compartments.  The  powder  charge  containers  can  be  lifted  out  with- 
out the  aid  of  straps. 

The  front  compartment  is  equipped  with  a  steel  door  which  is 
hinged  at  the  bottom  and  swings  downward  when  opened.  The 
rear  compartment  is  equipped  with  an  armor-plate  door  hinged  at 
its  lower  edge,  and  when  opened  hangs  vertically  downward.  The 
front  door  when  opened  downward  is  supported  by  the  footboard 
in  a  horizontal  position.  Each  door  when  closed  is  held  in  position 
by  latches  provided  on  the  sides  of  the  chests,  which  swing  over  and 
engage  steel  handgrips  riveted  on  either  edge  of  the  door  at  the  top. 


221 

Extending  above  the  chest  at  the  front  on  either  side,  handrails 
are  provided.  The  rails  are  constructed  of  steel  and  are  provided 
with  leather  guards.  The  rails  fit  into  small  brackets  rivited  to  the 
chest  sides,  and  may  be  dismounted  from  the  chest  by  removing  the 
retaining  pins.  Three  grip  straps  are  also  fastened  to  the  upper  front 
edge  of  the  chest  to  assist  the  personnel  when  mounting  the  vehicle. 

Straps  are  provided  with  the  usual  fastenings  at  the  top  of  the  chest 
to  accommodate  the  soldiers'  personal  equipment,  and  also  picket 
ropes  at  the  rear.  At  the  front  of  the  chest  the  fastenings  accommo- 
date blankets,  lamps,  and  tool  cases.  On  either  side  of  the  chest 
fastenings  are  provided,  the  left  side  accommodating  a  saw  in  a 
leather  case,  and  the  right  side  a  spanner  wrench. 

The  frame  consists  of  two  flanged  sides  connected  by  cross  stays 
to  the  draft  pole,  which  consists  of  two  flange  steel  members  extending 
back  the  length  of  the  vehicle.  The  outside  rails  are  provided  with 
flanges  and  holes  through  which  the  axle  passes.  The  chest  is  mounted 
on  the  frame,  the  axle  brackets  on  the  chest  corresponding  with  the 
flanges  on  the  side  rails,  making  a  solid  bearing  for  the  axle,  which 
is  held  in  place  by  keys. 

Forward  of  the  chest,  across  the  side  rails,  a  wooden  footboard  and 
platform  is  provided.  Suspended  below  the  footboard  on  either  side 
is  a  fuze  locker,  which  provides  carrying  compartments  for  30  fuzes, 
15  in  each  locker.  Each  locker  is  provided  with  a  door,  which  swings 
downward  when  opened,  and  each  is  equipped  with  a  hasp  and  a 
pivot  thumb  lock. 

Suspended  from  the  platform  to  the  rear  of  the  right  fuze  locker, 
a  tin  box,  containing  3  pounds  of  grease,  is  strapped. 

The  frame  is  provided  at  the  rear  with  a  steel  prop  which  swings 
up  to  the  right  side  of  the  frame  and  is  retained  in  this  position  by  a 
spring  clip  when  in  traveling  position. 

Wire-net  receptacles  are  suspended  under  the  rear  section  of  the 
frame  on  either  side  of  the  prop  bracket.  The  receptacles  provide 
space  for  canvas  watering  buckets  and  ropes. 

The  draft  pole,  which  is  an  extension  of  the  center  rail  of  the  frame, 
is  joined  at  its  extreme  forward  end  by  a  lunette,  which  engages 
the  pintle  on  the  ammunition  wagon  limber  when  in  traveling  posi- 
tion. A  pole  prop  is  also  provided  for  supporting  the  draft  pole 
when  the  wagon  is  unlimbered.  The  prop  swings  up  to  a  horizontal 
position  when  the  wagon  is  in  traveling  position.  Attachments  on 
the  underside  support  a  jointed  draft  pole  and  a  handspike. 

Tire  brakes  are  provided  for  each  wheel,  the  brake  system  being 
operated  as  one  unit.  The  shoes  which  bear  against  the  wheel  are 
supported  by  brackets  fastened  to  the  side  rails  at  the  front. 


222 

The  shoes  are  operated  by  a  crank  located  on  the  left  rear  side  of 
the  vehicle  under  the  frame.  The  crank  is  connected  to  the  shoes 
by  rods  supported  on  the  frame. 

Wheels  of  the  wooden  type,  56  inches  in  diameter,  having  steel 
tires  3  inches  in  width,  are  provided  on  this  vehicle.  They  are 
retained  on  the  axle  by  means  of  an  adjusting  collar  and  linch  pin. 
The  bearing  is  protected  from  dirt  and  other  foreign  matter  by  a  dust 
cap  which  fastens  over  the  end  of  the  hub  box. 


AMMUNITION   WAGON  AND  AMMUNITION   WAGON    LIMBER.   LIMBERED. 

Drag  washers  are  provided  on  each  wheel  to  which  ropes  may  be 
fastened  to  assist  in  the  maneuvering  of  the  vehicle. 

Weights,  dimensions,  etc. 

Weight  of  wagon,  empty pounds--  1,  732 

Weight  of  wagon,  loaded  and  equipped do 3,  556 

Pressure  of  wagon  pole  on  limber  pintle,  loaded do 

Pressure   of   wagon   pole    on    limber  pintle    with    two    men  on  wagon, 

loaded pounds—      196 

Height  to  top  of  handrail feet—  5.  229 

Height,  handrails  removed do 4.  416 

Width,  maximum do 6.  291 

Length  of  wagon : do—  _  9.  708 

Greatest  projection  beyond  track  of  wheels .  —inches—  6.  25 

Wheel  track do 63 

Diameter  of  wheels—  do 56 


5-INCH,  60-POUNDER,  AMMUNITION  WAGON  LIMBER, 
MARK  II  (BRITISH). 


The  limber  comprises  the  frame  with  pintle;  ammunition  chest; 
fuze  locker;  draft  fittings;  wheels  and  axle. 

The  limber  is  designed  to  draw  the  ammunition  wagon  by  means 
of  the  pintle  provided  at  the  rear.  The  vehicle  is  equipped  for 
2-horse  draft.  It  carries  16  rounds  of  ammunition  together  with 
the  necessary  powder  charges.  Provision  is  also  made  to  carry 
43  fuzes.  28  of  which  are  carried  in  the  ammunition  chest,  and  the 
remainder  in  the  fuze  locker  fastened  to  the  top  of  the  chest.  Imple- 
ment fastenings  are  fastened  on  the  exterior  of  the  chest  and  foot- 


FRONT   VIEW   OF   AMMUNITION    WAGON    LIMBER. 

board,  and  accommodate  rifles,  blankets,  and  the  customary  tools 
and  accessories. 

The  chest  is  constructed  of  steel  and  is  provided  at  the  rear  with 
three  doors.  The  interior  of  the  chest-  is  subdivided  by  two  steel 
plates  into  three  main  divisions,  access  to  each  being  at  the  rear. 

Each  division  is  separated  by  cross  plates  into  four  rows  of  com- 
partments, the  lower  two  rows  of  each  division  being  subdivided  into 
smaller  compartments  to  accommodate  a  total  of  eight  high  ex- 
plosive and  eight  shrapnel  shells. 

55160—21 1  r,  (  _>•_>:} ) 


224 

The  two  upper  rows  of  the  two  outside  divisions  are  constructed 
to  accommodate  a  total  of  16  powder  charges,  each  protected  by 
tin  containers. 

The  two  upper  rows  of  compartments  in  the  middle  division  accom- 
modate a  tray  for  small  stores,  such  as  cotton  waste,  pins,  pliers,  and 
other  small  tools;  and  2  fuze  boxes,  each  containing  14  fuzes.  The 
fuze  boxes  occupy  the  upper  row  of  compartments. 

The  powder-charge  containers  and  the  shell  are  retained  in  place 
in  the  chest  by  quick-release  straps,  and  the  shells  are  withdrawn 


REAR  VIEW  OF   AMMUNITION   WAGON   LIMBER. 

from  the  compartments  by  withdrawing  straps  and  blocks,  identical 
with  those  on  the  ammunition  wagon. 

A  door  is  provided  at  the  rear  of  the  chest  for  each  main  com- 
partment. The  two  outer  doors  are  of  armor  plate  and  have  hinges 
at  the  bottom  edges,  and  when  opened  hang  down  vertically  from 
the  chest.  A  small  armor-plate  apron  is  hinged  to  each  door  at  its 
upper  edge.  The  aprons  hang  vertically  from  the  door  when  each 
door  is  opened,  and  form  an  extension  toward  the  ground,  thereby 
giving  additional  protection  for  the  personnel  serving  the  gun. 
When  the  door  is  in  closed  position,  the  aprons  fold  down  over  the 
outside  of  the  door  and  are  retained  in  position  by  latches  fastened 


225 
• 

to  the  upper  part  of  the  chest,  which  engage  steel  hand  grips  riveted 
to  the  aprons. 

The  middle  compartment  is  equipped  with  a  steel  door  which  is 
hinged  at  the  upper  edge,  and  when  opened,  rests  over  the  top  of  the 
chest.  The  spring  latches  with  thumb  lift  grips  are  riveted  to  the 
door  which  engages  suitable  latches  on  the  lower  edge  of  the  chest 
when  the  door  is  in  the  closed  position.  Two  small  clips  which 
extend  over  the  edge  of  the  side,  at  the  lower  sides,  act  as  retainers 
for  the  outer  odors  when  they  are  closed. 

In  operation  the  middle  door  is  first  opened,  thereby  removing  the 
clips  which  bear  against  the  outside  doors,  allowing  the  outer  doors 
to  be  swung  open.  In  closing  the  chest  the  two  outer  doors  are 
closed  first. 

Handrails,  protected  by  leather,  are  provided  on  either  side  of  the 
chest,  and  extend  above  the  chest.  They  engage  suitable  brackets 
riveted  to  the  chest,  to  which  they  are  fastened  by  pins.  By  the 
removal  of  the  retaining  pins,  the  handrails  may  be  dismounted  from 
the  chest. 

The  exterior  of  the  chest  is  fitted  with  implement  fastenings  and 
straps,  the  front  plate  having  spring  catches  for  three  rifles.  Three 
grip  straps  are  fastened  to  the  upper  edge  of  the  chest  at  the  front, 
to  assist  the  personnel  in  riding  on  this  vehicle. 

Three  leather  pockets,  one  on  the  rear  middle  door  and  one  on 
either  side  of  the  chest,  are  provided  for  carrying  fuze  and  limber 
keys. 

A  wooden  locker  for  carrying  fuzes  is  fastened  by  steel  straps  to  the 
top  of  the  chest  on  the  left  side.  The  locker  is  equipped  with  a  lift 
lid,  hinged  at  the  front  and  provided  with  a  hasp  and  thumb  lock  at 
the  front.  The  interior  is  constructed  to  carry  15  fuzes.  Two 
blankets,  which  serve  as  a  seat  cushion,  are  strapped  to  the  top  of 
the  chest  at  the  front,  and  the  soldiers'  personal  equipment  is  strapped 
at  the  rear. 

Each  side  of  the  chest  has  riveted  thereto  a  steel  bracket,  which 
extends  below  the  chest  body,  and  is  provided  with  an  opening 
through  which  the  axle  passes. 

The  frame  which  supports  the  ammunition  chest  consists  mainly 
of  two  side  rails,  two  middle  rails,  and  the  connecting  cross  rails. 

The  middle  rails  are  connected  at  the  front  of  the  frame  to  form  a 
seat  for  the  wooden  horse  pole.  The  outer  rails  converge  slightly  at 
the  front,  and  with  the  middle  rails  form  a  support  for  the  wooden 
platform  and  footboard.  Two  of  the  cross  rails  extend  across  the 
frame,  directly  beneath  the  edges  of  the  chest,  giving  a  solid  support 
to  which  the  chest  is  fastened.  The  other  cross  rail  extends  across 
the  extreme  front  of  the  frame  and  is  fitted  with  hooks  for  the  sup- 
port of  two  singletrees.  A  wooden  horse  pole,  equipped  with  a  neck 
yoke  bar,  is  provided. 


226 

• 

Forward  of  the  chest  a  wooden  footboard  and  platform  is  fastened 
to  the  upper  side  of  the  frame.  The  boards  have  staples  for  the 
accommodation  of  leather  straps,  which  secure  rope  lashings,  shovels, 
and  other  similar  equipment  to  the  footboards. 

On  the  under  forward  right  side  of  the  frame  a  case  is  provided  to 
carry  a  bolo.  On  the  left  side  of  the  frame,  in  a  corresponding  posi- 
tion, a  case  is  provided  to  carry  a  water  brush. 

Suspended  from  under  the  wooden  platform,  on  the  left  side,  is  a 
box  containing  3  pounds  of  grease.  Under  the  right  side  of  the 
platform,  fastenings  are  provided  to  carry  two  cans  containing  lubri- 
cating oil. 

A  pintle,  which  engages  the  lunette  on  the  draft  pole  of  the  ammu- 
nition wagon,  is  provided  in  the  frame  at  the  rear. 

In  each  side  rail  at  the  rear  a  hole  is  provided  which  forms  a  bear- 
ing for  the  axle.  The  steel  axle  bracket  on  the  sides  of  the  chest 
correspond  with  these  holes,  and  form  a  solid  bearing  for  the  axle, 
which  is  held  in  place  by  keys. 

Wheels  of  the  wooden  type,  56  inches  in  diameter,  having  steel  tires 
3  inches  in  width,  are  provided.  An  adjusting  collar  and  linchpin 
screws  the  wheel  to  the  axle.  Protection  against  the  ingress  of  dirt 
and  foreign  matter  is  provided  by  a  dust  cap  which  fastens  over  the 
end  of  the  hub  box. 

Drag  washers  to  assist  in  the  maneuvering  of  the  vehicle  are  pro- 
vided on  each  wheel. 

The  wheels  and  axle  of  the  limber  are  interchangeable  with  those 
on  the  ammunition  wagon.  No  brake  is  provided  on  the  ammunition 
wagon  limber. 

Weights,  dimensions,  etc. 

Weight  of  limber,  empty -.pounds—     1,  410 

Weight  of  limber,  loaded  and  equipped do 2,632 

Weight  of  wagon  and  limber,  empty do__        3, 148 

Weight  of  wagon  and  limber,  loaded do 6,188 

Weight  of  limber  only,  with  wagon  limbered  up,  empty do 1.  486 

Weight  of  limber  only,  with  wagon  limbered  up,  loaded do 2,  730 

Weight  of  limber  pole  at  position  of  center  tug  hole  with  wagon  limbered 

up,  loaded,  without  men pounds —          14 

Weight  of  limber  pole  at  position  of  center  tug  hole  with  wagon  limbered 

up,  loaded,  with  2  men  on  limber  only pounds — 

Weight  of  limber  pole  at  position  of  center  tug  hole  with  wagon  limbered 

up,  with  2  men  on  limber  and;  2  men  on  wagon pounds 25 

Length  of  limber  with  pole feet__  14. 166 

Length  of  limber  without  pole do 5.  5 

Length  of  limber  and  wagon,  over  all do 22.  687 

Length  between  axles  of  limber  and  wagon do 8.  25 

Height  of  limber  to  top  of  handrails do__        5.  666 

Height  of  limber,  handrails  removed do 4.  895 

Width  of  limber,  maximum do 6.291 

Wheel  track  of  limber inches 63 

Diameter  of  wheels  of  limber do 56 

Diameter  of  turning  circle  of  limber  and  wagon feet 23.  5 


155-MILLIMETER  .HOWITZER  MATERIEL,  MODEL  OF  1917 

(SCHNEIDER). 


Experience  indicated  the  necessity  of  artillery  of  larger  caliber 
than  the  75-millimeter,  having  a  longer  range  and  better  character- 
istics, yet  mobile  enough  to  permit  its  use  as  a  supplementary  weapon. 
This  necessitj-  led  to  the  adoption  of  the  155-millimeter  caliber,  as  the 
more  suitable  105-millimeter  caliber  was  not  available  then.  The 
importance  of  this  155-millimeter  howitzer  is  evident  when  it  is 
realized  that  it  is  the  largest  weapon  at  the  present  time  that  can  be 
used  by  combat  divisions,  and  is  especially  valuable  for  use  against 
strongly  intrenched  infantry  and  in  counter  battery  firing. 

The  type  of  155-millimeter  howitzer  carriage  adopted  is  known  by 
the  French  as  the  155-millimeter  Court  Schneider,  model  of  1917,  and 
by  the  United  States  as  the  155-millimeter  howitzer  carriage,  model  of 
1918  (Schneider).  The  howitzers  manufactured  in  the  United  States 


RIGHT   SIDE   VIEW   OF   CARRIAGE   IN   TRAVELING   POSITION. 

are  also  distinguished  from  those  made  in  France  by  the  designation 
''Model  of  1918."  The  American  materiel  differs  from  the  French 
in  having  a  straight  shield  instead  of  a  curved  one,  rubber  instead 
of  steel  tires,  a  slightly  different  firing  mechanism,  and  several  other 
minor  changes.  The  howitzer  is  mounted  on  a  carriage  having  a 
single  trail  composed  of  two  pressed  steel  flasks.  At  the  front  end 
these  are  connected  by  the  axle  housing  and  at  the  rear  by  a  fixed 
spade.  The  carriage  embodies  many  ingenious  features  designed  to 
reduce  the  weight  and  insure  stability. 

The  recoil  mechanism  is  of  the  hydropneumatic  type,  the  sleigh 
recoiling  with  the  howitzer.  In  recoiling  the  liquid  is  forced  from  one 
side  of  the  piston  to  the  other  through  a  variable  orifice,  which  gradu- 
ally closes  until  the  howitzer  is  brought  to  a  stop.  The  return  of 

(227) 


228 


229 

the  howitzer  into  battery  is  effected  by  the  expansion  of  the  air  com- 
pressed during  recoil.  The  length  of  recoil  is  practically  constant, 
and  in  order  to  allow  the  howitzer  to  be  fired  at  high  elevations 
without  digging  in  the  trail  the  trail  is  made  of  a  curved  shape. 


FRONT    VIEW   OF    CARRIAGE   IN    BATTERY. 

By  sliding  transversely  along  its  axle  the  howitzer  is  capable  of 
traversing  through  a  total  angle  of  6°.  Its  maximum  elevation  is 
approximately  42°.  It  fires  a  95-pound  projectile  with  a  muzzle 
velocity  of  about  1,480  feet  per  second  to  a  maximum  range  of  about 
12,300  yards.  Separate  loading  ammunition  is  employed.  By  the 
use  of  the  reduced  powder  charges,  shorter  ranges  are  reached  with 


SIDE   VIEW   OF   CARRIAGE   EN   ROUTE. 

steep  angles  of  fall  and  with  less  wear  on  the  gun.     Its  life,  before 
relining  is  necessary,  is  approximately  7.000  rounds. 

The  entire  equipment  is  horse-drawn  and  the  equipment  for  each 
howitzer  includes  a  carriage  limber,  used  when  traveling  to  support 
the  trail,  three  caissons  or  ammunition  vehicles,  and  a  number  of 
repair  and  supply  trucks. 


230 


155-MILLIMETER  HOWITZER  MATERIEL,  MODEL  OF  1918 

(SCHNEIDER). 


The  155-millimeter  howitzer,  model  of  1918  (Schneider),  is  of  the 
hydropneumatic  long-recoil  type,  which  may  be  used  for  direct  fire, 
but  was  specially  designed  for  indirect  fire.  On  account  of  its  high 
trajectory  it  is  able  to  direct  shells  on  targets  inaccessible  to  field 
guns  of  limited  elevation. 

This  howitzer  has  given  satisfactory  results  in  actual  service  and 
has  proven  to  be  superior  to  other  howitzers  of  similar  caliber.  It 
has  a  muzzle  velocity  of  1.480  feet  per  second  and  attains  a  maximum 
range  of  12,300  yards,  the  projectile  weighing  approximately  95 
pounds. 

A  maximum  rate  of  fire  of  four  rounds  per  minute  may  be  attained, 
but  heating  as  well  as  difficulty  of  preparing  and  serving  of  ammuni- 
tion by  the  gun  crew  renders  such  rate  impossible  for  any  length  of 
time,  however.  The  normal  rate  of  fire  is  two  per  minute. 

The  howitzer  is  mounted  on  a  sleigh  and  rigidly  secured  by  a 
breech  key  and  a  holding-down  band.  The  sleigh  contains  the  recoil 
mechanism  which  permits  long  recoil  and  insures  stability  at  low 
elevations.  When  the  gun  is  fired,  the  sleigh  recoils  on  bronze  slides 
on  the  cradle,  which  is  a  U-shaped  steel  plate  and  rests  on  the  trunnion 
bearing  of  the  trail. 

This  howitzer  may  be  elevated  from  zero  to  42°  by  means  of  the 
elevating  mechanism.  The  traverse  is  52.5  mils  to  the  right  and  left, 
the  carriage  sliding  on  the  axle  and  pivoting  on  the  spade,  which 
prevents  the  carriage  from  recoiling  when  the  gun  is  fired.  The 
customary  shield  affords  protection  for  the  gunners  from  shrapnel 
and  flying  fragments. 

In  traveling  position  the  howitzer  is  retracted  and  locked  to  the 
cradle,  the  cradle  locked  to  the  trail,  and  the  spade  revolved  and  se- 
cured to  the  bottom  of  the  trail.  The  lower  end  of  the  trail  rests  on  the 
carriage  limber,  which  is  used  to  carry  its  proportionate  share  of  the 
load  of  the  howitzer  and  carriage  in  traveling  position.  The  limber 
is  equipped  with  a  connecting  pole  for  motor  traction.  The  carriage 
and  limber  wheels  are  rubber  tired  and  considered  able  to  travel  over 
any  roads  suitable  for  field  artillery. 

This  materiel  consists  of: 

The   155-millimeter  howitzer   and    carriage,   model   of    1918 

(Schneider). 
The  155-millimeter  howitzer  carriage  limber,   model   of  1918 

(Schneider). 

The  155-millimeter  howitzer  caisson,  model  of  1918. 

(231) 


232 


g 

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233 

The  howitzer,  carriage,  and  limBer  are  of  French  design  and  were 
manufactured  in  the  United  States. 

The  caisson  is  of  American  design  and  manufacture.  This  materiel 
is  used  with  motorized  batteries,  and  a  full  complement  of  tractors 
and  trucks  is  provided  for  the  transportation  and  service  of  the 
battery. 

The  cart,  model  of  1918,  and  reel,  model  of  1909  MI,  described 
with  the  75-millimeter  materiel,  are  also  used  with  this  materiel. 

Weights,  dimensions,  ballistics,  etc. 

Weight  of  howitzer,  including  breech  mechanism pounds—     2,690 

Caliber inches—      6.10 

Total  length do 91. 0 

Weight  of  projectile pounds—          95 

Weight  of  maximum  powder  charge do 8 

Muzzle  velocity  of  shell feet  per  second 1,476 

Muzzle  velocity  of  shrapnel : 

Minimum do 666 

Maximum do 1,  434 

Maximum  range  of  shell yards 12,250 

Maximum  range  of  shrapnel do 10,700 

Weight  of  howitzer  and  carriage,  fully  equipped pounds—     7,600 

Weight  of  carriage  complete,  but  without  equipment do 4,  729 

Diameter  of  carriage  wheels inches—          53 

Width  of  carriage  track do 60 

Normal  length  of  recoil do 51.  30 

Elevation 0°  to  42°  20 

Maximum  traverse 3°  (52$  mils)  right  and  3°  (52$  mils)  left. 

Weight  of  limber,  completely  equipped pounds—     1,  440 

Diameter  of  limber  wheels inches 42.  82 

Width  of  limber  track do 61 

Turning  angle  of  155-millimeter  howitzer,  limber  and  carriage  limbered 

degrees 52 


234 


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235 


155-MILLIMETER  HOWITZER  AND  CARRIAGE,  MODEL  OF 
1918  (SCHNEIDER). 


The  howitzer  is  of  the  built-up  type  and  consists  of  a  tube  hav- 
ing a  jacket  shrunk  over  its  rear  half.  The  breech  end  is  equipped 
with  a  counterweight  which  is  fitted  with  leveling  plates  to  be  used 
with  a  gunner's  quadrant  when  setting  elevations.  Below  the  breech 
recess  is  the  bridle  which  couples  the  gun  to  the  sleigh  and  on  the 
forward  end  of  the  howitzer  a  holding  down  band  also  functions  to 
secure  the  tube  to  the  sleigh. 

The  breech  mechanism  is  of  the  plastic  obturator  type  with  an 
interrupted  screw  type  breechblock.  The  breechblock  is  hinged  at 
the  right  and  by  means  of  one  motion  of  the  breech  lever  can  be  ro- 
tated and  swung  clear  of  the  breech. 

The  forward  mushroom-shaped  head  of  the  breechblock  is  equipped 
with  a  flexible  asbestos  ring  known  as  the  obturator  pad.  The  gas 
check  pad  or  plastic  obturator  is  composed  of  a  mixture  of  one  part 
asbestos  and  three  parts  nonfluid  oil,  contained  in  a  canvas  cover- 
ing. The  pad  is  protected  by  the  small,  front,  and  rear  split  rings. 
A  steel  filling-in  disk  is  placed  between  the  gas  check  pad  and  the 
breechblock.  On  firing,  the  asbestos  ring  is  compressed  and  acts  as 
a  gas  check  to  prevent  the  leakage  of  powder  gases  back  through  the 
breech.  The  asbestos  pad,  by  its  shape,  causes  the  split  rings  to 
spread  when  pressure  is  applied  on  the  mushroom  head.  It  has 
sufficient  resiliency  to  resume  its  original  form  after  firing. 

The  firing  mechanism  is  of  the  French  percussion  primer  type. 
The  primer  is  fired  by  means  of  the  firing  pin  driven  forward  by  a 
hammer  operated  by  the  lanyard.  The  firing  pin  is  supported  in 
the  firing  mechanism  block,  which  is  unscrewed  each  time  a  new 
primer  is  inserted.  A  safety  device  is  used  in  connection  with  the 
firing  mechanism  block,  which  makes  it  impossible  to  unlock  the 
breech  while  the  block  is  in  position,  or  to  insert  the  block  while  the 
breech  is  unlocked.  The  firing  mechanism  block  is  interchangeable 
with  those  used  in  the  following  weapons: 

155-millimeter  gun,  model  of  1918  (Filloux). 
8-inch  howitzer  (Vickers  Mark  VI  and  VIIIJ). 
240-millimeter  howitzer,  model  of  1918  (Schneider). 

The  recoil  mechanism  is  of  the  hydropneumatic  long  recoil  type. 
With  this  howitzer  the  type  of  recoil  is  known  as  constant,  i.  e.,  the 
length  of  recoil  is  not  shortened  at  high  elevations.  The  sleigh 
contains  the  recoil  mechanisms  and  serves  as  a  support  for  the 

(236) 


237 


238 


239 

howitzer,  being  secured  to  it  by  the  breech  lug  and  the  holding 
down  band.  On  recoiling,  howitzer  and  sleigh  move  on  the  cradle 
fastened  to  the  trunnions  of  the  carriage,  the  piston  rods  remaining 
stationary. 

A  mixture  of  glycerine,  water,  and  caustic  soda  is  used  in  the 
recoil  brake  and  counterrecoil  mechanism.  The  gas  used  in  the 
counterrecoil  mechanism  may  be  either  air  or  nitrogen. 

Nitrogen  is  always  used  when  available,  as  it  has  no  corrosive 
action  on  the  mechanism.  The  energy  of  recoil  is  absorbed  by  the 
friction  of  the  liquid  while  passing  through  the  openings  in  and 
around  the  recoil  piston  and  by  the  compression  of  the  nitrogen  in 
the  cylinders.  The  howitzer  is  returned  to  battery  by  the  energy 
stored  in  the  compressed  nitrogen  which  forces  the  liquid  out  and 
reacts  against  the  counterrecoil  piston.  When  in  battery,  the  initial 
nitrogen  pressure  is  approximately  485  pounds  per  square  inch,  which 
is  sufficient  to  hold  the  howitzer  in  battery  at  all  angles  of  elevation. 
Gages  are  provided  to  indicate  both  the  quantity  of  liquid  and  the 
nitrogen  pressure.  Suitable  pumps  are  provided  with  the  materiel 
for  pumping  in  liquid  and  air.  Cylinders  of  compressed  nitrogen 
are  carried  to  replenish  the  supply  of  nitrogen. 

The  cradle  is  secured  in  the  trunnions  of  the  carriage  and  supports 
the  sleigh  during  recoil.  To  the  underside  of  the  cradle  are  fastened 
two  elevating  arcs  by  which  the  howitzer  is  elevated  by  means  of  the 
handwheel  located  on  the  left  side  of  the  carriage.  Elevations 
from  Oc  to  42°  20'  may  be  obtained. 

The  traverse  of  the  carriage  is  obtained  by  the  traversing  mech- 
anism causing  the  carriage  to  slide  on  the  axle,  the  trail  pivoting  on 
the  spade.  The  movement  is  3°  each  side  of  the  center,  or  a  total 
of  105  mils.  The  movement  is  obtained  by  means  of  a  traversing 
nut  rigidly  fastened  to  the  axle,  causing  a  traversing  screw  to  travel 
carrying  the  carriage  along  the  axle.  The  carriage  travels  along  the 
axle  on  rollers  mounted  on  Belleville  springs.  When  the  gun  is 
fired,  the  springs  are  compressed  and  the  carriage  rests  on  the  axle. 
A  lock  is  provided  for  relieving  the  strain  on  the  traversing  and 
elevating  mechanisms  when  traveling.  Two  traversing  handwheels 
are  provided,  one  on  each  side  of  the  carriage. 

The  wheels  are  of  wood,  1,350  millimeters  (53  inches)  in  diameter 
and  are  fitted  with  solid  rubber  tires.  The  carriage  is  equipped 
with  a  pair  of  brakes  acting  directly  on  the  rubber  tires.  An  armor- 
plate  shield  for  the  protection  of  the  personnel  against  small  arms 
and  shrapnel  fire  is  also  provided. 

Sighting  is  accomplished  by  means  of  a  quadrant  sight,  panoramic 
sight,  and  peep  sight. 
55160—21 16 


240 


241 


242 

The  quadrant  sight,  model  of  1918  (Schneider),  is  mounted  on  the 
left  trunnion  of  the  carriage.  It  is  used  for  laying  the  piece  in 
elevation.  The  angle  of  site  mechanism  is  combined  with  this  sight. 
Mounted  on  the  top  of  the  quadrant  sight  is  the  United  States  pano- 
ramic sight  for  laying  the  piece  in  traverse.  An  extension  bar  is 
provided  for  use  with  the  panoramic  sight  to  enable  the  sight  to  be 
raised  enough  to  see  over  the  shield  or  other  obstructions  in  direct 
aiming. 

The  peep  sight,  used  only  in  direct  fire,  or  in  emergency,  may  be 
mounted  on  the  quadrant  sight  in  place  of  the  panoramic  sight. 

Two  complete  sets  of  night  sighting  equipment  are  provided  for 
use  when  firing  at  night.  When  not  in  use  these  equipments  are 
packed  in  cases  provided  for  that  purpose  and  carried  on  the  carriage 
limber.  The  night  lighting  equipment  consists  principally  of  a  chest, 
an  aiming  lamp,  an  azimuth  lamp,  a  portable  lamp,  and  the  necessary 
cables  and  fixtures. 


155-MILLIMETER  HOWITZER  CARRIAGE  LIMBER,  MODEL 
OF  1918  (SCHNEIDER). 


The  155-millimeter  howitzer  carriage  limber  is  a  two-wheeled 
vehicle  employed  to  support  the  trail  of  the  carriage  when  traveling. 
This  limber  consists  of  a  built-up  steel  frame  mounted  on  wheels 
and  axle.  It  has  no  chests  and  provides  no  seats  for  the  personnel. 

The  pintle  is  riveted  to  the  extreme  rear  end  of  the  frame  and 
serves  as  a  bearing  for  the  lunette  of  the  carriage  when  the  howitzer 
is  limbered.  Additional  support  for  the  trail  is  provided  by  a  trail 
rest  riveted  in  front  of  the  pintle  and  on  which  the  fifth  wheel  of  the 
trail  bears. 

Hooks  are  provided  for  carrying  a  picket  rope,  and  small  boxes 
for  carrying  grease  and  the  night  lighting  equipment  are  secured  on 
the  frame. 

A  prop  is  provided  on  the  front  of  the  frame  for  holding  the 
limber  up  when  not  en  route.  The  standard  short  pole  with  the 
lunette  for  motor  traction  batteries  is  provided,  or  the  long  pole  may 
be  substituted  for  horse-drawn  equipment. 

The  wheels  are  of  wood  construction,  1,240  millimeters  (48.82 
inches)  in  diameter,  with  solid  rubber  tires. 

Weight  and  principal  dimensions. 

Weight    of    limber   empty pounds__  1,  227 

Weight  of  limber  completely  equipped do 1,440 

Weight  of  limber  and  carriage,  limbered _do 8,  930 

Weight  on  ground  under  each  wheel,  with  carriage  limbered do 1,  380 

Weight  of  each  wheel \lo 335 

Diameter  of  wheels inches—  48.82 

Width  of  track do 61 

Turning  angle  of  limber  and  howitzer  carriage,  limbered degrees 52 

NOTE. — The  weight  of  this  carriage  limber  equipped  with  horse  pole  is  prac- 
tically the  same  as  with  motor  pole. 

(243) 


244 


TREE  OWH  EYE 
LONGITUDINAL  SUPPORT 

OMTR/IL 
SUPPORT  AUXILIARY  BRACKET 

TUOm.  SUPPORT  TEBAR 
SAFETY  CHAIM 
5ATETY  CHAJM  CROSS  BAR 

PLATE. 
PLATE 


CASE  TOANSVtRSE  SUPPORT 


155  MM.  HOWITZER  CARRIAGE  LIMBER. 

MODEL  OF  1918  (SCHNEIDER). 

PLAN  AND  RIGHT  SIDE  VIEWS 


0       I00200.W0400500600W0800TOIOOOIIOO  1200    1500  MOO      MLUMETER5 


155-MILLIMETER  HOWITZER  CAISSON,  MODEL  OF  1918. 


The  155-millimeter  howitzer  caisson  is  a  two-wheeled,  spring- 
supported  vehicle  for  the  transportation  of  ammunition.  Normally 
it  is  a  motorized  vehicle,  two  caissons  forming  a  train  drawn  by  one 
tractor.  However,  by  removing  the  connecting  pole  and  substitut- 
ing the  standard  pole  the  front  vehicle  of  the  train  can  be  converted 
into  a  horse-drawn  caisson  limber.  Any  caisson  in  the  battery 


REAR  VIEW  OF  CAISSON. 

except  the  caisson  equipped  with  the  hand  reel  can  be  so  converted 
into  a  caisson  limber.  The  caisson  carries  14  complete  rounds  of 
ammunition  and  2  extra  powder  charges  for  the  155-millimeter 
howitzer. 

The  chest  is  made  up  of  the  lower  and  upper  chest  body  and  rear 
plate,  which  is  of  armor  plate.  The  chest  is  divided  into  an  upper 
and  lower  compartment,  the  opening  between  them  forming  a  space 
for  the  axle,  pole  socket,  and  pintle  bracket,  and  houses  the  fuze  box 
and  oil  can. 

The  upper  compartment  is  arranged  for  the  transportation  of 
8  projectiles  and  16  powder  charges.  Powder  is  served  to  the 
caissons  in  fiber  containers,  each  containing  2  powder  charges.  The 

(245) 


246 


247 

container  is  fitted  with  an  air-tight-joint  metal  cover  and  base.  The 
lower  compartment  is  arranged  for  the  transportation  of  6  projectiles. 
The  upper  chest  door  when  closed  forms  a  cover  for  the  chest  and  is 
held  open  by  door  props.  When  open,  this  armor  plate  door  serves 
as  a  shield  for  the  cannoneers. 

The  lower  compartment  is  also  provided  with  an  armor  plate  door 
hinged  to  the  bottom  of  the  chest  body,  and  has  an  armor  plate 
apron  hinged  to  its  edge.  When  open,  the  lower  chest  door  and 
apron  hang  down,  forming  a  shield  for  the  cannoneers.  When 
closed,  this  door  forms  a  cover  for  the  lower  compartment ;  the  apron 
doubles  back  against  the  lower  chest  door  and  is  latched  in  place. 

Both  compartments  are  provided  with  loose  diaphragms,  by  the 
use  of  which  the  caisson  can  be  made  available  for  transporting  any 
of  the  following  types  of  shells  : 

155-millimeter  common  steel  shell,  Mark  I; 

155-millimeter  common  steel  shell,  Mark  II; 

155-millimeter  shrapnel,  Mark  I ; 

155-millimeter  common  steel  shell.  Mark  IV ; 

Semi-steel  shell,  Mark  XVII. 

Only  one  type  of  shell  can  be  carried  in  the  same  compartment  at 
one  time.  When  carrying  either  common  steel,  gas.  or  shrapnel,  the 
loose  diaphragms  are  placed  in  position  after  the  projectiles  are 
inserted  in  the  projectile  tubes.  When  the  doors  are  closed  (with 
either  common  steel  or  gas  shells)  the  door  stiffeners  bear  against 
the  bases  of  the  projectiles,  holding  them  in  place.  With  shrapnel 
the  edges  of  the  flanged  holes  in  the  loose  diaphragm  bear  against 
the  rotating  bands  of  the  projectiles.  When  used  to  transport  com- 
mon steel  shells  Mark  IV  the  loose  diaphragms  are  placed  inside  the 
body  of  the  caisson  next  to  the  front  diaphragms.  When  the  doors 
are  closed  the  door  stiffeners  bear  against  the  bases  of  the  projectiles, 
holding  them  firmly  against  the  loose  diaphragms. 

Foot  rests,  handrails,  and  grip  straps  are  provided  on  the  chest 
for  the  convenience  of  its  personnel.  The  outside  of  the  chest  is 
provided  with  implement  fastenings  for  the  usual  complement  of 
accompanying  tools  and  accessories.  Blanket  straps  are  provided  on 
top  of  the  chest  for  carrying  the  blanket  rolls  of  the  battery  person- 
nel ;  provision  also  is  made  on  top  of  the  chest  for  carrying  the  con- 
necting pole  and  on  the  rear  for  carrying  the  lunette  and  caisson 
prop  when  used  as  a  horse-drawn  vehicle. 

The  caisson  prop  when  down  serves  to  support  the  front  end  of 
the  caisson ;  in  traveling  it  is  swung  up  and  held  by  the  prop  chain. 

The  axle  passes  through  the  caisson  between  the  upper  and  lower 
intermediate  plates.  Axle  brackets  are  clamped  on  either  end  of  the 
axle  just  outside  of  the  chest,  and  rotation  or  lateral  motion  of  the 
chest  is  prevented  by  clamp  screws  and  Belleville  springs.  The  chest 


248 

has  a  spring  suspension  similar  to  that  of  the  4.7-inch  gun  caisson, 
model  of  1917,  for  lightening  road  shocks. 

The  caisson  is  provided  with  a  brake  mechanism  of  the  band  type. 
The  brake  drums  are  mounted  on  the  hub  boxes  of  the  wheels  and 
the  band  brakes  lined  with  Raybestos.  A  brake  lever  secured  to  a 
bracket  riveted  to  the  caisson  body  functions  as  a  means  by  which 
the  brakes  may  be  applied. 

The  caisson  is  usually  equipped  with  the  short  pole  for  motor 
traction,  but  the  pole  socket  is  designed  so  that  the  long  pole  may  be 
used  when  it  is  desired  to  use  the  vehicle  as  a  horse-drawn  limber.  A 


FRONT  VIEW  OF  CAISSON. 

standard  pintle  is  fitted  at  the  rear  for  the  connection  of  the  other 
vehicles. 

One  caisson  in  each  battery  is  equipped  with  a  reel  for  caisson, 
model  of  1917.  This  is  a  hand-operated  reel  for  the  transportation 
and  handling  of  telephone  wire.  (See  page  168.) 

Weights  and  Dimensions. 

Over-all   length inchea 79 

Over-all  width do 78.  5 

Over-all  height do 67 

Weight  without  equipment  (unloaded) pounds 2,345 

Weight   fully   equipped    (unloaded) do 2,447 

Weight  completely  equipped  and  loaded do 3,  949 

Weight  of  reel  caisson  completely  equipped  and  loaded do 4,  006 

Width  of  track inches__  60 

Diameter  of  wheels do 60 

Turning  diameter  of  two  caissons feet 18 


155-MILLIMETER  GUN  MATERIEL,  MODEL  OF  1918 

(FILLOUX). 


The  type  of  155-millimeter  field  gun  adopted  is  known  by  the 
French  as  the  "G.  P.  F."  (Grande  Puissance  Filloux),  and  by  the 
United  States  as  the  model  of  1918.  This  caliber,  which  corresponds 
to  6-inch  artillery,  is  the  heaviest  mobile  artillery,  exclusive  of  the 
heavy  howitzers  and  the  railroad  artillery. 

This  monster  weapon  is  of  rugged  design,  combining  mobility  and 
power,  and  has  a  large  horizontal  training  angle  to  render  it  suitable 
for  the  concentration  of  artillery  fire  at  long  ranges.  No  other  avail- 
able weapon  of  equivalent  caliber  can  be  considered  to  rival  this  type. 


TRAVELING  POSITION    (RIGHT   SIDE). 

This  piece  is  especially  valuable  in  firing  against  captive  balloons, 
counter  battery  firing,  and  interdiction. 

The  Filloux  gun  is  mounted  on  a  carriage  having  a  split  trail  of 
box  girder  section,  which  is  spread  out  when  in  action,  the  ends  of 
the  trail  being  firmly  anchored  by  spades  in  the  ground.  The  split- 
trail  effect  permits  clearance  for  recoil  at  high  elevations  and  allows 
firing  over  a  horizontal  field  of  60°  and  an  elevation  varying  from 
0°  to  35°. 

Its  muzzle  velocity  is  about  2,411  feet  per  second,  a  rate  of  propul- 
sion that  throws  its  projectile,  weighing  95  pounds,  approximately 
17,700  yards,  or  a  little  more  than  10  miles. 

The  gun  recoils  in  slides  formed  in  the  cradle  which  rests  in  the 
trunnions  of  the  top  carriage.  The  length  of  recoil  is  automatically 
controlled  and  varies  with  the  elevation,  while  the  counter  recoil  is 
pneumatic.  The  entire  recoil  mechanism  is  commonly  called  the 
recuperator  and  is  supported  on  the  carriage  at  its  trunnions.  When 

(249) 


250 


251 

traveling,  the  trail  is  closed  up  and  the  ends  thereof  are  supported  by 
a  carriage  limber  provided  with  a  steering  gear  brake,  and  drawn^ 
by  a  tractor.    In  traveling  position  both  carriage  and  carriage  limber 
are  supported  on  semielliptical  springs  to  absorb  all  road  shocks 

and  vibrations. 


PREPARING    CARRIAGE    FOR    BATTERY    POSITION. 

The  life  of  the  gun  before  relining  becomes  necessary  is  about 
3,000  rounds  and  maximum  rate  of  fire  is  two  rounds  per  minute. 
The  entire  equipment  is  motorized.  A  carriage  limber,  which  sup- 
ports the  trails  in  traveling,  accompanies  each  gun.  Caissons  are 
not  used  with  these  guns,  the  ammunition  being  carried  in  motor 
trucks  or  cargo  carriers. 


CARRIAGE   IN   TRAVELING   POSITION    (REAR  VIEW). 

155-millimeter  gun  materiel,  model  of  1918  (Filloux),  consists  of: 
155-millimeter  gun  and  carriage,  model  of  1918. 
155-millimeter  gun  carriage  limber,  model  of  1918. 

The  above  materiel  is  of  French  design  and  of  both  French  and 
American  manufacture. 


252 


253 

Weights,  dimensions,  ballistic*,  etc. 

Weight  of  gun,   including   breech   mechanism pounds 8,795 

Length  of  gun inches—  232.  87 

Caliber do 6. 1042 

Muzzle  velocity __feet  per  second 2,411 

Rifling:  One  turn  in  2,989  caliber,  right  hand,  uniform. 

Weight   of   projectile pounds—  95 

Maximum  range    (Mark   III   shell   at  39°    elevation) yards 17,700 

Weight  of  maximum  powder  charge pounds—  25$ 

Weight   of   carriage   only do 11,065 

Weight  of  gun  and  carriage  complete do 19,860 

Diameter  of  wheels millimeters 1, 160 

Width  of  track do 2, 250 

Height  of  axis  of  gun  from  ground do 1,  482 

Range  of  elevation degrees 0   to  35 

Maximum   traverse do 60 

Weight  of  gun  carriage  and  limber pounds 23,050 

Weight  of  limber  complete do 3, 190 

The  distance  from  center  line  of  carriage  axle  to  center  line  of  limber 

axle,  approximately millimeters 4, 500 


155-MILLIMETER  GUN  AND   CARRIAGE,  MODEL  OF  1918 

(FILLOUX). 


The  gun,  models  of  1918  and  1918  MI,  is  of  the  built-up  type, 
consisting  of  a  tube  strengthened  by  a  ring,  jackets,  hoops,  and 
the  muzzle  bell.  All  details  except  the  firing  mechanism  provide 
interchangeability  of  parts  with  the  155-millimeter  (G.  P.  F.)  guns 
of  French  manufacture.  A  recoil  lug  on  the  under  side  of  the  breech 
ring  provides  means  of  attaching  the  recoil  and  recuperator  rods. 
Bronze  clips  to  serve  as  guides  in  the  cradle  are  secured  to  the  sides 
of  the  jackets. 


MAXIMUM    ELEVATION    OF    GUN. 

The  breechblock  is  of  the  interrupted- screw  type,  having  four  plain 
and  four  threaded  sectors.  The  breech  mechanism  is  of  the  plastic 
obturator  type,  having  the  forward  mushroom-shaped  head  of  the 
breechblock  equipped  with  an  asbestos  ring  known  as  the  obturator 
pad.  Upon  firing,  this  ring  is  compressed  and  acts  as  a  gas  check 
to  prevent  the  leakage  of  powder  gases  through  the  breech.  It  has 
sufficient  resiliency  to  resume  its  original  form  after  firing.  The 
firing  mechanism  is  of  the  French  percussion  primer  type  described 
under  "155-millimeter  Schneider  howitzer,"  page  236,  and  is  inter- 
changeable with  the  guns  enumerated  therein. 

The  cradle  is  a  steel  forging  bored  with  three  parallel  cylinders  for 
housing  the  recoil  brake  and  recuperator,  and  is  pivoted  by  trunnions 
in  the  trunnion  bearings  of  the  top  carriage.  On  the  upper  side  of 
the  cradle  are  slots  for  the  gun  slides,  and  to  its  lower  side  the  elevat- 
ing rack  is  bolted. 

(254) 


255 


55160—21 


256 


257 

The  recoil  mechanism  is  of  the  hydropneumatic,  variable  recoil 
type.  The  larger  of  the  three  cylindrical  bores  in  the  cradle  block 
contains  the  recoil  mechanism;  the  two  smaller  ones,  the  parts  of 
the  recuperator  mechanism. 

This  mechanism  consists  of  a  piston  and  piston  rod  and  a  control 
rod.  The  piston  rod  is  connected  to  the  breech  lug  and,  therefore, 
recoils  with  the  gun.  Grooves  of  variable  depth  are  milled  along  the 
length  of  the  control  rod,  controlling  the  flow  of  oil  through  the 
ports  of  the  piston  during  recoil.  The  control  rod  assembles  within 
the  bore  of  the  piston  rod,  and  does  not  move  longitudinally,  but 
rotates.  The  amount  of  this  rotating  changes  the  area  of  the  orifices 
through  which  the  oil  can  pass.  Its  rotation  is  accomplished  by  means 
of  an  arm  and  gear  sectors  in  such  a  manner  as  to  shorten  the  recoil 
as  the  gun  elevates.  I 


CARRIAGE   IN   FIRING   POSITION. 

A  replenisher  or  gravity  tank  is  provided  in  connection  with  the 
recoil  cylinder  which  assures  the  recoil  cylinders  being  full  at  all 
times  and  also  takes  care  of  any  expansion  of  the  oil  due  to  heating. 
Its  capacity  is  about  17  quarts. 

The  recuperator  mechanism  consists  of  two  connected  cylinders, 
one  containing  the  piston  and  piston  rod  which  are  attached  to  the 
breech  lug,  while  the  other  contains  a  mushroom  valve  and  a  dia- 
phragm. The  diaphragm  separates  the  oil,  contained  in  the  first 
cylinder  and  part  of  the  second  cylinder,  from  the  high-pressure  air, 
which  compels  the  return  of  the  gun  into  battery  after  recoil.  Nor- 
mally a  small  amount  of  oil  must  be  between  the  valve  and  diaphragm. 
Oleonapthe  is  the  liquid  used  in  this  recoil  mechanism.  The  amount 
of  oil  in  the  recoil  and  recuperator  "mechanism  is  shown  by  indicators, 
so  that  it  can  always  be  seen  whether  or  not  they  need  filling. 


258 


259 

The  top  carri((</<'  is  a  steel  casting  mounted  on  the  bottom  carriage, 
on  which  it  pivots  to  traverse  the  piece.  Belleville  springs  carry  the 
weight  of  the  gun  when  traversing,  but  on  firing  the  springs  compress 
and  the  firing  stresses  are  taken  on  the  bearing  surfaces  between  the 
top  and  bottom  carriage. 

The  tipping  parts  are  carried  on  the  trunnions  of  the  top  carriage, 
which  also  houses  the  elevating  and  traversing  mechanism  and  permits 
high  angle  of  elevation  for  the  cradle. 

The  bottom  <'<iri-'«i(/c  is  a  steel  casting  suspended  from  the  axle  (in 
traveling  position)  by  a  heavy  multiple  leaf  spring.  It  supports  the 
top  carriage,  houses  the  axle,  and  provides  hinge  connections  for 
the  trail.  When  firing  the  axle  is  unshackled  from  the  springs  and 
the  bottom  carriage  bears  directly  on  the  axle. 

Ti'dversing  is  accomplished  by  rotation  of  the  top  carriage  on  the 
bearing  surface  of  the  bottom  carriage  by  means  of  a  rack  and  train 


ACCESSORIES   AND   CATERPILLAR   WHEEL   SHOES. 

of  gears  which  are  operated  by  the  handwheel  on  the  left  side  of  the 
carriage.  A  traverse  of  60° — 30°  right  and  30°  left — is  possible. 

Elevating  is  accomplished  by  a  rack  on  the  cradle  operated  through 
gears  by  the  handwheel  located  on  the  gear  box  at  the  left  of  the  top 
carriage.  Elevations  from  0°  to  35°  are  obtainable. 

The  trail  is  of  the  split  type  and  consists  of  steel  plate  beams  of 
box  section.  Locks  are  pivoted  at  the  forward  end  of  the  trails  for 
securing  them  in  the  open  position.  When  brought  together  they  are 
clamped,  and  attached  to  the  limber.  A  traveling  lock  is  provided 
on  the  trail  for  retaining  the  gun  in  retracted  position.  Two  types 
of  spade  are  provided,  one  for  soft  and  one  for  hard  ground.  When 
traveling  the  spades  are  always  removed  from  the  trail. 

The  wheels  are  of  cast  steel,  each  wheel  having  two  solid  rubber 
tires,  and  are  equipped  with  the  usual  band  brakes.  Caterpillar 
wheel  shoes  for  traveling  over  soft  ground  are  provided,  which  as- 
semble over  the  rubber  tires.  They  consist  of  12  plates  for  each 
wheel,  which  give  a  broad  bearing  surface  under  the  wheel. 


260 


261 

The  sighting  equipment  is  exactly  the  same  as  that  described  under 
the  155-millimeter  Schneider  howitzer,  except  the  difference  in  the 
bracket  as  indicated  on  page  239. 

Ammunition  used  is  of  the  separate  loading  type,  the  projectile 
weighing  95  pounds  and  the  charge  25  pounds.  Either  shrapnel  or 
high-explosive  steel  shell  is  used,  as  well  as  gas  shells  and  other 
special  ammunition.  The  propelling  charge  of  smokeless  powder 
is  a  sectionalized  charge  made  up  of  two  sections — a  base  charge  and 
one  smaller  increment. 

The  fuzes  commonly  used  are  the  31-second  combination  fuze  for 
use  with  shrapnel  and  combining  time  and  percussion  elements,  the 
point  detonating  fuze  Mark  IV  used  with  the  steel  high  explosive 
shell,  and  the  Mark  II  point  detonating  fuze  used  with  gas  shell. 

CATERPILLAR  ADAPTERS. 

Caterpillar  tracks  similar  to  those  used  on  trailer  caissons,  re- 
placing the  road  wheels  on  gun  carriages  or  other  normally  wheeled 
vehicles  are  being  tried  out.  The  adapters  are  attached  to  the  car- 
riage axle,  the  purpose  being  to  greatly  decrease  the  unit  ground 
pressure.  The  adapter  should  not  be  confused  with  bands  consisting 
of  wood  or  metal  shoes  which  are  sometimes  placed  over  gun  car- 
riage wheels  to  decrease  the  unit  ground  pressure. 


CATERPILLAR   ADAPTER   FOR   155-MM.   GUN,   G.   P.   F.,   MODEL    1918. 


The  adapters  and  wheels  of  this  gun  carriage  are  interchangeable. 
The  unit  ground  pressure  when  using  wheels  is  41  pounds  per  square 
inch ;  that  with  the  adapters,  10  pounds.  In  addition  to  the  experi- 
mental adapters  on  hand,  sufficient  are  being  constructed  to  equip  the 
weapons  of  one  battery  for  more  extended  service  test. 


262 


155-MILLIMETER  GUN  CARRIAGE  LIMBER,  MODEL  OF  1918 

(FILLOUX). 


The  carriage  limber  is  a  two-wheeled  vehicle  designed  to  support 
and  secure  the  rear  ends  of  the  trails  and  to  provide  a  coupling 
attachment  to  the  tractor  when  transporting  the  carriage.  The 
principal  parts  are  the  wheels,  axle,  steering  mechanism,  frame, 
springs,  and  seat. 

The  axle  is  very  similar  to  the  usual  design  of  front  axles  of  auto- 
mobiles. It  is  of  I-beam  section,  having  forked  ends  with  axle  arms 
pivoted  therein,  providing  a  means  of  steering.  By  means  of  a  drag 
link  and  steering  lever  pivoted  at  the  center  of  the  frame  and  con- 
nected to  the  steel  pole,  steering  is  accomplished. 


FRONT   VIEW   OF   LIMBER   EN   ROUTE. 

The  frame  or  clamp  for  holding  the  gun  trail  in  position  is  mounted 
on  the  axle  by  means  of  two  semielliptical  multiple-leaf  springs.  The 
upper  cross  beam  of  this  frame  has  a  seat  bolted  to  it  for  the  brake- 
man,  who  operates  the  gun-carriage  brake  when  en  route  by  means  of 
a  lever  acting  through  a  wire  rope.  The  wheels  are  identical,  and 
interchangeable,  with  the  wheels  of  the  gun  carriage. 

Weights  and  dimensions. 

Weight  complete pounds 3,190 

Weight  with  carriage  and  gun do 23,  050 

Weight  of  carriage  on  limber  (traveling  position) do 6,490 

Width  of  track  (center  to  center  of  tires) millimeters —  2,250 

Free  height  und'er  limber  and  carriage  (traveling  position) do 250 

Diameter  of  wheels do 1, 160 

Height  of  seat  cushion  from  ground  (seat  assembled  on  top  of  trails, 

traveling  position) millimeters--  1,550 

Distance  from  center  line  of  carriage  axle  to  center  line  of  limber  axle 

trails  on  limber) millimeters 4,500 

(263) 


264 


6-INCH  GUN  MATERIEL,  MODEL  OF  1917   (BRITISH). 


The  6-inch  gun  materiel,  model  of  1917,  is  British  throughout, 
being  designed  and  manufactured  in  England.  It  consists  of  a  6-inch 
gun,  Mark  XIX,  mounted  on  an  8-inch  howitzer  carriage,  Mark  VII, 
known  as  the  6-inch  gun  carriage,  Mark  VIIIA.  This  Mark  XIX 
gun  is  of  wire-wound  construction,  having  a  muzzle  velocity  of  2,500 
feet  per  second  and  a  range  of  19,650  yards. 

The  gun  body  is  of  steel  and  consists  of  tubes,  a  series  of  layers  of 
steel  wire,  jacket,  breech  bush,  and  breech  ring.  The  breech  ring  is 
prepared  for  the  reception  of  the  breech  mechanism  and  is  provided 
with  a  lug  on  the  underside  for  the  attachment  of  the  hydraulic 
buffer  and  recuperator  of  the  carriage. 

The  breech  mechanism  is  operated  by  means  of  a  lever  on  the  right 
side  of  the  breech.  On  pulling  the  lever  to  the  rear  the  breech  screw 
is  automatically  unlocked  and  swung  into  the  loading  position. 
After  loading,  one  thrust  of  this  lever  inserts  the  breech  screw  and 
turns  it  into  the  locked  position.  The  breech  mechanism  is  similar 
to  that  used  on  the  8-inch  howitzers,  both  in  design  and  operation. 

The  firing  mechanism  is  of  the  percussion  type  and  is  not  inter- 
changeable with  other  British  guns.  The  firing  mechanism  is  de- 
signed for  percussion  firing,  and  is  so  arranged  that  the  gun  can  not 
be  fired  until  the  breech  screw  is  locked  and  the  breech  mechanism 
lever  home. 

The  only  changes  necessary  on  the  8-inch  howitzer  carriages 
(p.  279)  for  mounting  this  6-inch  gun  are:  The  rear  extension  plug, 
which  connects  the  gun  to  the  recoil  mechanism,  is  modified  and  the 
cut-off  gear  is  set  differently  to  shorten  the  recoil  when  in  action. 
The  firing  platform  and  all  of  the  accompanying  vehicles  of  the 
8-inch  howitzer  materiel  are  used. 

Ammunition  of  the  separate  loading  type  is  used,  both  shrapnel 
and  shell  being  issued. 

Weights,  dimension*,  and  ballistics. 

Materiel  of  gun,  steel  wire  wound. 

Length  of  gun inches 219 

Weight  of  gun  with  breech  mechanism pounds—  10,248 

Weight  of  gun  without  breech  mechanism do 9,  940 

Rifling,  uniform  one  turn  in  30  calibers. 

Weight  of  shell  or  shrapnel do 100 

Weight  of  powder  charge  (maximum) do 23 

Weight  of  powder  charge  (reduced) 15  pounds  7$  ounces 

(265) 


266 


5  5 


267 


268 

Maximum  range: 

Full  charge yards- _  19,  650 

Reduced  charge do 17,  570 

Muzzle  velocity : 

Full  charge feet  per  second--     2,500 

Reduced  charge do 2,  350 

Maximum  elevation degrees—          38 

Weight  of  carriage  only pounds 12,548 

Weight  of  gun  and  carriage  (fully  equipped) do 22,796 


7-INCH  NAVAL  TRACTOR  MOUNT,  MARK  V. 


The  7-inch  naval  tractor  mount,  Mark  V,  is  a  mobile,  track-laying 
field  piece  bearing  a  7-inch,  45-caliber  naval  rifle.  Projectiles  weigh- 
ing 153  pounds  may  be  fired  at  angles  of  elevation  varying  from 
horizontal  to  40°,  and  at  the  maximum  elevation  the  extreme  range 
obtainable  25,000  yards. 

The  chamber  diameter  of  the  gun  is  8.5  inches  and  the  distance  from 
the  face  of  the  tube  to  the  base  of  the  projectile  is  54.39  inches.  The 
volume  of  the  powder  chamber  is  3,369  cubic  inches.  The  maximum 
charge  consists  of  60  pounds  of  smokeless  nitrocellulose  powder, 
which  produces  the  maximum  service  pressure  of  17  tons  per  square 
inch.  Under  these  conditions  a  muzzle  energy  of  8,315  foot-tons  is 


CARRIAGE  AND   LIMBER   IN  TRAVELING  POSITION    (FRONT  VIEW). 

imparted  to  the  153-pound  projectile,  the  muzzle  velocity  being  2,800 
feet  per  second. 

The  recoil  mechanism  is  of  the  hydraulic  type,  the  gun  being  re- 
turned to  battery  by  a  pneumatic  counterrecoil  system.  The  recoil 
system  consists  of  a  simple  hydraulic  brake,  the  energy  of  recoil  being 
absorbed  through  a  distance  of  32  inches  by  forcing  a  mixture  of 
glycerine  and  water  through  orifices  of  gradually  decreasing  diameter 
cut  in  the  head  of  a  piston  operating  in  the  recoil  cylinder. 

The  method  of  reducing  the  size  of  the  orifices  is  interesting.  The 
recoil  piston  has  holes  bored  through  it  to  allow  the  liquid  to  pass 
from  one  side  to  the  other  when  the  piston  starts  to  move  back  when 
the  gun  is  fired.  Tapered  throttling  rods  enter  the  holes  in  the  piston 
head,  and  as  the  piston  moves  back  the  size  of  the  orifice  is  gradually 
diminished.  The  area  of  the  orifices  is  so  calculated  that  a  constant 
retardation  is  given  to  the  gun,  and  it  is  brought  to  rest  at  the  end  of 
the  stroke. 

(269) 


270 

The  counterrecoil  mechanism  adopted  on  this  mount  is  similar  to 
the  counterrecoil  mechanism  of  the  French  type,  as  used  on  155- 
millimeter  guns.  In  this  type  of  mechanism  when  the  gun  is  fired, 
a  piston  attached  to  the  gun  yoke  moves  backward  in  an  air-tight 
cylinder  containing  air  at  a  pressure  of  several  hundred  pounds  per 
square  inch,  still  further  compressing  the  air.  The  air  pressure  acting 
on  the  counterrecoil  piston  when  the  gun  has  reached  the  end  of  the 
recoil  brings  the  gun  back  into  battery  or  firing  position. 

The  counterrecoil  system  which  is  used  on  this  mount  is  located  on 
the  top  of  the  gun,  and  has  been  changed  into  a  combination  of  three 
cylinders,  connected  at  the  lower  end  by  a  bronze  head.  The  piston 
attached  to  the  yoke  operates  in  the  central  cylinder.  The  system 


REAR   VIEW   OF   CARRIAGE. 

of  liquid  packing  retained,  but  simplified,  and  the  entire  system  is 
well  adapted  to  American  machining  methods. 

A  traversing  gear,  incorporated  in  the  carriage  trail,  permits  of 
limited  training  either  side  of  the  center  line.  When  a  greater  range 
of  training  is  desired,  the  trail  is  either  shifted  on  the  ground  or  the 
carriage  is  mounted  upon  a  firing  platform  which  provides  for  train- 
ing through  a  firing  angle  of  60°.  A  shell-loading  tray,  which  rests 
on  the  carriage  trail,  is  used  to  load  shells  into  the  breech. 

The  elevating  gear  consists  of  a  simple  combination  of  a  hand- 
wheel,  worm  gear,  and  rack  and  pinion.  The  sighting  arrangements 
for  the  gun  consist  of  a  standard  panoramic  field  sight  fitted  to  a 
bracket  attached  to  the  gun  carriage. 


271 


The  track  layer,  which  is  of  the  double-tread  caterpillar  type,  is 
designed  to  carry  the  mount  over  practically  any  kind  of  ground 
likely  to  be  encountered  in  service.  The  proportions  of  the  chain 
tracks  are  such  as  to  produce  a  pressure  of  about  14  pounds  per 
square  inch  upon  the  soil  during  transportation,  which  is  approxi- 
mately half  that  exerted  by  a  horse.  The  track  layer  also  serves  as  a 
stand  or  foundation  for  the  mount  during  action. 

A  caterpillar  tractor  is  used  to  draw  this  vehicle  from  one  position 
to  another.  A  limber  hooked  between  the  mount  and  the  tractor 
supports  the  trail  during  transit;  during  action  the  limber  and  the 
tractor  are  withdrawn  from  the  immediate  field  of  danger. 

The  limber  wheels  are  carried  on  taper  axles  and  are  equipped  with 
grease  cups  for  lubricating  purposes.  A  pintle  and  lunette  are  pro- 
vided on  the  axle  in  case  it  is  desired  to  attach  an  ammunition  or 
supply  trailer  for  transportation.  The  limber  is  connected  to  the 


LEFT  SIDE  VIEW   OF  CARRIAGE   IN   BATTERY. 

mount  by  means  of  a  swivel-pole  which  is  pivoted  on  the  limber 
connection  of  the  trail. 

The  firing  platform  provides  a  durable  and  substantial  foundation, 
adaptable  to  various  soil  conditions  and  light  enough  to  permit  of 
easy  and  convenient  transportation.  The  firing  platform  includes  a 
forward  table,  upon  which  the  track  layers  rest,  and  a  rear  thrust 
beam  to  which  the  trail  is  secured  by  suitable  pins.  The  rear  thrust 
beam  is  made  in  two  sections,  which,  when  combined,  provide  for 
training  through  an  arc  of  60°.  One  section  may  be  used  alone  if 
desired.  Training  is  accomplished  by  shifting  the  trail  around  the 
arc  of  the  platform  to  the  set  of  pin  holes  nearest  the  desired  angle. 
Accurate  adjustments  in  training  are  made  with  the  traversing  gear. 

The  7-inch  naval  tractor  mount  is  so  designed  that  its  weight  is 

almost  entirely  supported  by  the  track  layers,  but  a  small  percentage 

of  the  weight  being  carried  on  the  trail.     When  the  mount  is  being 

pulled  along  an  upgrade  of  appreciable  slope,  the  center  of  gravity 

55160—21 18 


272 

is  shifted  and  the  weight  of  the  gun  may  have  a  tendency  to  throw 
the  trail  in  the  air. 

To  preclude  any  such  occurrence,  eyebolts  are  secured  to  the  gun 
yoke,  which  are  used  to  draw  the  recoiling  parts  back  sufficiently 
to  bring  about  equilibrium. 

Track  grousers  may  be  bolted  to  the  track  shoes  when  there  is 
likelihood  of  the  mount  slipping  sidewise  during  transport  on  hill- 
sides, in  an  actual  road  test  this  gun  was  pulled  over  rough  ground 
and  proved  able  to  cover  any  ground  over  which  the  tractor  itself 
was  able  to  operate.  Obstructions  were  mowed  down,  and  yet  the 
entire  weight  of  the  gun  was  so  evenly  and  well  distributed  that  no 
damage  was  done  to  the  roads.  The  mount  functioned  perfectly, 
remaining  steady  on  the  point  of  aim  during  continued  firing.  The 
caterpillar  treads,  locked  in  position  by  the  brake,  were  as  steady  as  a 
concrete  foundation. 


7-INCH  GUN,  MARK  II  AND  CARRIAGE,  MARK  V. 


The  T-inch,  45-caliber,  naval  rifle  is  built  up  of  a  tube,  hoops,  and 
locking  rings.  When  erosion  destroys  the  effectiveness  and  accuracy 
of  the  gun  it  may  be  rebuilt  by  boring  out  the  tube  and  shrinking  in 
a  conical  nickel-steel  liner.  The  gun,  without  the  breech  mechanism, 
weighs  12.81  tons,  while  the  weight  of  gun  and  breech  mechanism  is 
28,700  pounds.  The  rifling  is  right  hand  of  hook  section  and  consists 
of  28  grooves  and  lands,  having  an  increasing  twist  from  zero  at  the 
origin  to  one  turn  in  25  calibers  at  a  point  22  inches  from  the  muzzle. 
The  remainder  of  the  twist  is  uniform.  The  gun  is  the  heaviest  and 
hardest  hitting  gun  for  which  a  mobile  field  mount  has  been  requested 
by  our  Army. 


CARRIAGE   AND   LIMBER   IN   TRAVELING   POSITION    (REAR   VIEW). 

The  carriage  which  supports  the  gun  is  a  structural  steel  frame- 
work built  up  of  standard  shapes,  consisting  essentially  of  two  steel 
trunnion  bearing  plates  cross  braced  at  each  end  to  form  a  single 
unit  with  a  central  well  into  which  the  gun  recoils.  These  side 
girders  are  riveted  to  the  carriage  trail.  The  carriage  and  trail 
forming  a  rigid  unit,  are  supported  on  the  carriage  axle  which  turns 
in  hubs  mounted  in  the  truck  frames  of  the  track  layer. 

On  the  left-hand  side  of  the  carriage  is  arranged  the  mechanism 
for  elevating  and  depressing  the  gun.  The  traversing  gear,  which 
provides  means  for  training  2°  either  side  of  the  center  line,  is  incor- 
porated in  the  rear  section  of  the  trail.  This  gear  consists  of  a  steel 
plate  resting  on  the  ground  underneath  the  trail ;  a  worm  shaft  oper- 
ated by  ratchet  wrenches  shifts  the  trail  with  reference  to  the  plate 
and  enables  the  gun  to  be  accurately  trained. 

(273) 


274 

Navy  guns  do  not  carry  trunnions  attached  directly  to  the  gun ;  they 
are  turned  on  the  outside  surface  of  a  gun  slide.  This  cylindrical 
gun  slide,  on  which  the  trunnions  are  attached,  carries  the  gun.  The 
trunnion  seats  are  placed  at  the  upper  end  of  the  carriage.  The 
recoil  and  counterrecoil  mechanisms  are  also  attached  to  the  gun 
slide,  operating  through  pistons  attached  to  the  yoke.  The  gun 
runs  in  and  out  of  the  gun  slide  when  recoiling,  bronze  liners  being 
fitted  to  the  inside  of  the  slide  to  enable  this  to  take  place  easily. 
The  trunnions  of  the  gun  are  mounted  sufficiently  high  so  that  at 
maximum  angles  of  elevation  only  a  shallow  trench  need  be  dug  to 
permit  clearance  for  the  recoil  of  a  gun. 


TOP   CARRIAGE   AND   AXLE   DETAILS. 


The  elevating  arc  segment,  meshing  with  the  pinion  of  the  elevat- 
ing mechanism,  is  bolted  to  a  pad  on  the  left-hand  face  of  the  slide. 
The  teeth  of  the  arc  are  cut  on  a  pitch  circle  concentric  with  the 
trunnion  centers  to  permit  of  a  40°  movement  of  the  slide  in  a  ver- 
tical plane,  starting  from  horizontal.  The  upper  and  lower  extremi- 
ties of  the  arc  are  fitted  with  limiting  stops  to  prevent  jamming. 

The  hydraulic  brake. — The  energy  of  recoil  is  checked  and  dissi- 
pated by  means  of  a  hj^draulic  brake  mounted  on  the  bottom  of  the 
slide.  This  mechanism  is  made  up  of  a  piston  operating  in  a  cylinder 
filled  with  liquid  and  rigidly  fixed  to  the  slide.  The  piston  is  at- 
tached to  the  gun  yoke  by  the  piston-  rod  which  passes  through  a 
stuffing  box  in  the  rear  end  of  the  cylinder.  Two  orifices  are  pro- 
vided in  the  piston  head  for  throttling  rods  which  are  arranged 
longitudinally  in  the  cylinder.  In  battery,  all  the  liquid  is  in  rear 
of  the  piston.  As  the  piston  recedes  during  recoil,  the  liquid  is 
forced  around  the  throttling  rods  through  the  orifices  in  the  piston 
to  the  forward  end  of  the  cylinder,  dissipating  the  energy  through 


275 

the  frictional  heat  generated.  The  cross  section  of  the  throttling 
rods,  around  which  the  liquid  must  flow  in  passing  through  the 
orifices,  is  such  that  a  pressure  approximately  uniform  is  exerted 
upon  the  liquid  throughout  the  period  of  recoil.  The  length  of  re- 
coil is  32  inches. 

Incorporated  in  the  cylinder  head  is  a  counterrecoil  chamber  into 
which  the  recoil  liquid  flows  during  recoil.  When  the  gun  is  brought 
back  to  battery  by  the  counterrecoil  mechanism,  its  momentum  is 


ASSEMBLED   VIEW   OF   HYDRAULIC   BRAKE. 

checked  through  the  action  of  a  counterrecoil  plunger,  mounted  on 
the  forward  face  of  the  piston,  as  it  enters  the  chamber  and  forces 
the  liquid  back  into  the  cylinder  through  the  orifice  between  the 
plunger  and  the  plunger  bushing  screwed  into  the  mouth  of  the 
chamber.  This  action  takes  place  during  only  the  last  14  inches  of 
counterrecoil  stroke. 

The  liquid  used  in  the  hydraulic  brake  consists  of  a  mixture  of  4 
parts  glycerine  and  1  part  water,  by  volume.  This  liquid  is  poured 
into  the  cylinder  through  a  filling  hole  on  the  right-hand  side  of  the 
cvlinder  head. 


276 

The  upper  portion  of  the  cylinder  head  is  arranged  to  form  an 
expansion  chamber  to  provide  for  the  expansion  of  the  liquid  which 
results  from  the  frictional  heat  generated  in  the  cylinder.  When 
expansion  of  the  liquid  takes  place  with  continued  firing,  the  in- 
creased volume  of  the  liquid  simply  compresses  the  air  in  the  expan- 
sion chamber  instead  of  acting  to  prevent  the  return  of  the  gun  to 
battery.  To  assure  the  presence  of  a  definite  amount  of  air  in  the 
expansion  chamber  at  all  times,  the  filling  hole  is  fitted  with  a  tube 
which  extends  down  into  the  chamber  and  traps  the  desired  volume  of 
air  when  the  cylinder  is  filled. 

Counterrecoil  system. — Energy  to  return  the  gun  to  battery  and  to 
maintain  it  in  that  position  at  all  angles  of  elevation  is  obtained  by 
means  of  a  pneumatic  counterrecoil  system,  mounted  on  the  top  of 


VIEW   OF   AXLE   MOUNTED   IN   TRACK   LAYER. 

the  slide.  A  piston,  operating  in  an  air  cylinder  and  connected  to 
the  gun  yoke  by  a  piston  rod.  serves  to  compress  the  air  within  the 
cylinder  when  the  gun  recoils.  At  the  end  of  recoil,  the  compressed 
air  acts  upon  the  piston  to  return  the  gun  to  battery.  On  either  side 
of  the  air  cylinder  and  connected  with  it  through  a  port  is  an  air 
tube  which  serves  as  a  reservoir. 

Since  it  is  necessary  for  the  counterrecoil  system  to  support  the 
weight  of  the  gun  and  breech  mechanism  against  gravity,  the  system 
is  charged  initially  with  air  at  300  pounds  per  square  inch,  gauge 
pressure.  This  pressure  assures  the  proper  functioning  of  the  coun- 
terrecoil mechanism  at  angles  of  elevation  up  to  approximately  34°. 
It  is  apparent  that  the  factor  of  gravity  decreased  with  the  angle  of 
elevation,  and  hence  less  pressure  is  required  to  bring  the  gun  to  bat- 
tery when  it  is  fired  at  angles  near  horizontal. 


277 

When  charged  to  340  pounds  pressure,  the  mechanism  will  func- 
tion properly  at  all  angles ;  however,  if  the  cylinder  should  be  charged 
only  to,  say,  225  pounds,  the  mechanism  may  be  relied  upon  to  return 
the  gun  to  battery  at  angles  of  elevation  up  to  23  or  24°.  To  insure 
return  of  the  gun  to  battery  when  firing  at  angles  above  34°,  air  cyl- 
inders should  be  charged  in  accordance  with  the  instructions,  and 
to  prevent  breakage  of  the  gauge  glass  and  to  preserve  the  accuracy 
of  the  instrument,  it  is  recommended  that  the  pressure  gauge  be  re- 
moved before  firing. 

The  elevating  gear  train  from  the  rack  on  the  slide  to  the  handwheel 
on  the  left  side  of  the  trail  is  made  up  of  a  pinion  and  shaft  in  mesh 
with  the  elevating  arc.  One  turn  of  the  elevating  handwheel  moves 
the  gun  56'  17"  in  elevation  or  depression. 

The  axle,  a  steel  forging  extending  across  the  width  of  the  carriage, 
is  supported  in  the  track  layer  by  a  hub  bracket  which  in  turn  is 
carried  by  the  structure  of  the  girder  on  which  the  sprocket  and  truck 


SIDE  ELEVATION  OF  TRACK   LAYER. 

wheels  are  mounted.  This  bracket  is  held  by  oscillating  bearings  and 
is  spring  supported  so  that  the  caterpillar  may  adjust  itself  to  any 
unevenness  in  the  road  when  the  gun  is  in  motion.  When  the  gun  is 
placed  in  firing  position,  the  springs  are  taken  up  by  means  of  holding 
down  screws  in  order  that  the  mount  may  keep  steadily  on  the  point  of 
aim  while  firing. 

The  function  of  the  hub  springs  is  to  impart  to  the  mount  a  degree 
of  resiliency  during  transit.  However,  when  firing,  resiliency  in  the 
mount  is  undesirable  and  often  dangerous,  thus  before  firing  the 
springs  are  compressed  until  the  hubs  bear  directly  upon  the  truck 
frames.  This  is  accomplished  by  means  of  adjusting  screws  screwed 
down  on  the  hub  bearing  blocks  until  the  springs  are  compressed  and 
the  hubs  rest  solidly  upon  the  truck  frames. 

The  track  itself  consists  of  an  endless  belt  of  cast-steel  links  con- 
nected by  hardened  pins,  each  link  carrying  a  corrugated  forged-steel 
plate  which  makes  contact  with  the  ground.  The  plates  overlap  when 
horizontal  so  that  a  continuous  surface  is  presented.  To  prevent  the 


278 

corrugated  surface  of  the  tread  from  slipping  in  soft  ground,  detach- 
able grousers  are  provided. 

The  track  links  run  over  a  large  idler  wheel,  a  sprocket  wheel, 
seven  truck  rollers,  and  four  track  rollers  on  each  caterpillar  track 
layer.  The  sprocket  wheels  carry  but  little  of  the  load  except  when 
the  gun  is  descending  a  grade  or  when  the  brake  is  applied  to  the 
mount.  For  smooth  running  and  reliability,  roller  bearings  are  fitted 
in  the  truck  and  idler  rollers,  the  ends  of  the  rollers  being  closed  by 
steel  plates  to  prevent  the  entrance  of  dirt  when  the  mount  is  hauled 
through  mud,  sand,  or  soft  earth.  A  brake  is  provided  to  permit 
control  of  the  mount  when  descending  hills  and  also  to  lock  the  cater- 
pillar in  position  when  the  gun  is  set  up  for  firing.  The  brake  con- 
sists of  a  toggle  joint  operating  on  the  rim  of  one  of  the  sprocket 
wheels,  the  tension  applied  being  controlled  by  an  adjustable  spring. 


CARRIAGE  IN  BATTERY  POSITION*,   SHOWING  MAXIMUM  ELEVATION  OF  GUN. 

Simple  as  the  brake  is  it  has  been  exceedingly  satisfactory  in  opera- 
tion in  controlling  the  heavy  mount  on  steep  grades  and  in  checking 
any  tendency  of  the  mount  to  move  on  firing. 

The  track  is  carried  around  two  track  idler  wheels  which  are  pro- 
vided with  bearings  mounted  on  the  extremities  of  the  track  frame. 
The  aft  idler  wheel  bearings  are  so  mounted  that  they  may  be  moved 
backward  or  forward  as  necessary  to  adjust  the  tension  and  to  take 
up  wear  on  the  links  and  shoes. 

Friction  brakes  operating  against  the  forward  idler  wheels  are 
mounted  on  the  truck  frames.  These  brakes  are  of  the  spring  release 
type  and  are  applied  by  means  of  handwheels  functioning  through 
yokes  and  levers  to  the  brake  shoes. 

The  quadrant  sight  (Schneider)  is  mounted  on  the  left  trunnion  of 
the  carriage  both  in  traveling  and  in  action. 


8-INCH  HOWITZER  MATfiRIEL  (VICKERS). 


The  characteristics  of  this  howitzer  are  a  compromise  between 
those  of  a  gun  and  a  mortar.  The  trajectory  is  classed  as  curved 
fire  and  the  useful  angles  of  elevation  and  resulting  angles  of  fall  lie 
between  15°  and  45°.  Inherently  a  long  life  of  the  piece,  favorable 
angle  of  fall  for  penetration,  a  small  zone  of  dispersion,  and  economy 
of  ammunition  result  and  may  be  said  to  be  the  advantages  of  the 
8-inch  howitzer;  the  range,  however,  is  not  great.  This  caliber  is 
mobile  in  a  sense,  but  there  are  limits  to  its  mobility.  When  these 
howitzers  have  to  be  transported  over  land  full  of  huge  craters, 
'with  the  roads  entirely  destroyed,  the  country  encumbered  with 
all  kinds  of  debris  and  frequently  reduced  to  a  sea  of  mud,  it  can  be 


easily  seen  why  a  successful  "  push "  usually  nets  a  considerable 
gain  in  captured  artillery.  If  the  trenches  give  way,  it  is  almost 
impossible  to  get  the  heavy  howitzers  away  quickly  enough  to  save 
them  from  being  captured  by  the  enemy. 

The  howitzer,  being  comparatively  short  when  compared  with  a 
gun  of  the  same  caliber,  is  capable  of  a  greater  angle  of  elevation 
than  the  same  caliber  of  gun.  The  chief  aim  of  the  howitzer  is 
to  destroy  incumbrance  such  as  trenches,  barbed  wire,  pill  boxes, 
and  the  like.  A  shell  that  travels  from  the  howitzer  ascends  at  a 
high  angle  and  drops  almost  vertically.  The  explosion  of  a  shell  so 
fired  is  much  more  effective  than  one  that  is  fired  with  only  a  slightly 
elevated  trajectory. 

(279) 


280 


281 


The  8-inch  howitzer,  being  mounted  on  a  wheeled  carriage  and 
not  having  to  be  disassembled  for  transporation,  is  much  more 
mobile  than  the  9.2-inch  or  240-millimeter  howitzer.  This  howitzer 
when  set  up  ready  for  firing  rests  on  and  is  braced  upon  a  firing  plat- 
form, which  is  transported  on  a  two-wheeled  wagon,  the  wagon  being 
attached  to  the  howitzer  carriage  and  drawn  as  part  of  the  unit 
with  the  carriage  and  limber  by  a  tractor.  On  reaching  the  spot 
selected  for  position  the  firing  platform  is  buried  flush  with  the 
surface  of  the  ground,  furnishing  a  steady  emplacement  from  which 
to  fire. 

The  8-inch  howitzer  materiel  is  called  the  "Vickers"  model  of 
1917,  of  which  there  are  in  use  two  types,  the  Mark  VI  and  Mark  VII, 
the  main  differences  between  the  Mark  VI  and  the  Mark  VII  being 
that  the  former  has  a  lower  muzzle  velocity  and  consequently  a  shorter 
range  than  the  latter,  also  that  the  Mark  VII  has  a  barrel  of  the  "  wire 
wound  "  construction,  whereas  the  Mark  VI  type  is  of  the  "  built  up  " 
construction.  The  Mark  VII  is  also  longer  and  heavier  than  the 
Mark  VI. 

The  Mark  VII  has  lately  been  superseded  by  a  Mark  VIIIJ,  the 
difference  between  the  two  being  that  the  powder  chamber  walls  of  the 
Mark  VII  proved  to  be  too  thin,  while  the  Mark  VIII£  overcomes 
this  defect  by  having  thicker  powder  chamber  walls.  Due  to  the 
fact  that  the  Mark  VIILJ  howitzer  has  a  greater  muzzle  velocity, 
and  consequently  a  greater  maximum  range  than  the  Mark  VI  by 
some  15  to  20  per  cent,  the  former  is  the  preferred  type. 

The  life  of  the  howitzers  before  relining  is  necessary,  varies  greatly. 
The  number  of  rounds  they  are  capable  of  firing  before  the  lining 
becomes  badly  worn  depends  on  whether  light  or  heavy  propelling 
charges  are  used.  The  use  of  light  propelling  charges  and  greater 
trajectory  elevation  to  get  the  desired  range  is  recommended,  rather 
than  heavy  charges  and  lower  elevation.  From  information  based  on 
actual  experience  the  average  life  of  the  8-inch  howitzer,  Mark  VI, 
is  7,800  rounds,  while  that  of  the  Mark  VIII£  is  3,000  rounds. 


Comparative  table  of  weights,  dimensions,  and  ballistics  for  8-inch  howitzers, 
Marks  VI  and  VIII$  and  6-inch  gun,  Mark  XIX. 


Mark  VI 
howitzer 
(Mark 
VI 
carriage). 

Mark 
VIIIJ 
howitzer 
(Mark 
VII 
carriage). 

Mark 
XIX 

gun 
(Mark 
VIII-A 
carriage). 

Weight  of  howitzer  or  gun,  including  breech  mechanism  — 
Weight  of  gun  or  howitzer  without  breech  mechanism  . 

pounds.. 
do.. 

6,552 
6,132 

7,730 
7,310 

10,248 
9,940 

Total  length  of  howitzer  or  gun    .             

inches.. 

127.6 

148.3 

219.22 

Length  of  howitzer  or  gun  

calibers.. 

15.9 

18.5 

86.5 

Distance  to  center  of  gravit  y  from  breech,  unloaded  

inches.. 

42.6 

50.5 

71.95 

Distance  to  center  of  gravity  from  breech,  loaded 

...do... 

42.3 

50.6 

71.65 

Length  of  bore  .                                 

do.... 

117.7 

138.4 

210.0 

Length  of  bore  .                 

calibers.. 

14.7 

17.3 

35.0 

Length  of  rifline  .  .  . 

...inches.. 

102.11 

99.52 

170.  75 

282 


283 


Comparative  table  of  weights,  dimensions,  and  ballistics  for  8-inch  howitzers, 
Marks  VI  and  F///$  and  6-inch  gun,  Mark  XIX — Continued. 


Mark  VI 
howitzer 
(Mark 
VI 
carriage). 

Mark 
VIIIJ 
howitzer 
(Mark 
VII 
carriage). 

Mark 
XIX 

gun 
(Mark 
VIII-A 
carriage). 

Number  of  grooves  

48 

48 

36 

Twist  (uniform) 

R.H.. 

1  in  15 

1  in  25 

linSO 

Travel  of  projectile  in  piece  

inches.  . 

104.96 

102.72 

174.0 

Weight  of  projectile 

.  .pounds.. 

200 

200 

100 

Weight  of  powder  charge. 

...do  

10.75 

17.5 

23.0 

Maximum  powder  uressure 

...do  

30,250 

30,240 

Muzzle  energv 

.  ...foot  tons.. 

2,345 

3,228 

3,308 

Muzzle  velocity  

feet  per  second  .. 

1,300 

1,525 

2,500 

Length  of  recoil  

inches.  . 

60-24 

52-24 

42-20 

Maximum  elevation     

degrees.. 

50 

45 

38 

Range  at  15  degrees  elevation  

yards.  . 

6,430 

7,400 

11,300 

Range  at  20  degrees  elevation 

...do..  . 

7,810 

8,900 

13,100 

Range  at  25  degrees  elevation  

...do... 

8,920 

10,500 

14,600 

Range  at  30  degrees  elevation  

...do... 

9,800 

11,540 

15,960 

Range  at  45  degrees  elevation 

.do  ... 

10,  710 

12,300 

Maximum  range  

do  

10,760 

12,600 

19,  650 

The  Mark  VI  howitzer  has  a  muzzle  velocity  of  1,300  feet  per 
second  and  a  maximum  range  of  10,760  yards  and  is  of  British  design 
and  of  both  British  and  American  manufacture.  The  Mark  VII 
howitzer  has  a  muzzle  velocity  of  1.525  feet  per  second  and  maximum 
range  of  12,600  yards  and  is  of  British  design  and  manufacture. 
The  Mark  VIII£  is  an  American  modification  of  the  British  wire- 
wound  Mark  VIII  howitzer  to  permit  of  a  built-up  type  of  construc- 
tion and  is  strictly  of  American  manufacture.  The  Mark  VIII^  has 
the  same  muzzle  velocity  and  range  as  the  Mark  VIII. 

Due  to  the  combination  of  British  and  American  manufacture, 
there  are  several  types  of  breech  mechanism  in  service;  the  two 
main  types  are  the  T  and  the  French  percussion  type. 

The  three  types  of  carriages  differ  but  slightly  in  design.  Each  is 
a  two-wheeled  vehicle  with  a  box-shaped  trail,  the  latter  being  cut 
away  to  provide  clearance  for  the  recoil  of  the  howitzer  or  gun  when 
fired  at  high  angles  of  elevation.  The  trails  of  the  Mark  VII  and 
VIIIA  types  are  modified  to  provide  a  larger  clearance  to  accommo- 
date the  Mark  VIII|  howitzer  and  Mark  XIX  gun  (see  p.  265)  and 
are  also  strengthened  to  withstand  the  greater  energy  of  recoil. 

The  howitzer  is  mounted  in  a  cradle  in  which  it  is  free  to  recoil 
under  the  control  of  a  hydraulic  recoil  cylinder.  After  recoil  it  is 
returned  to  firing  position  by  means  of  a  pneumatic  recuperator. 
The  carriage  permits  of  firing  at  high  angles  of  elevation,  and  as  the 
elevation  is  increased  the  length  of  recoil  is  proportionally  decreased 
by  a  cut-off  gear  fitted  to  the  cradle  and  buffer  in  order  that  the 
howitzer  will  not  strike  the  trail  or  ground  when  fired.  The  recoil 
mechanism  is  of  the  hydropneumatic  type  with  a  variable  recoil 
mechanism  which  lessens  the  length  of  recoil  the  greater  the  elevation 
given  the  howitzer  or  gun.  The  liquid  used  in  the  mechanism  is 
British  buffer  oil. 


284 

The  elevating  mechanism  permits  a  movement  of  50°  maximum 
elevation  for  the  Mark  VI  carriage,  45°  for  the  Mark  VII  carriage, 
and  38°  for  the  Mark  VIII A  carriage. 

The  cradle  pivots  on  its  trunnions  and  rests  in  bearings  provided 
in  the  top  carriage,  which  in  turn  is  pivoted  at  its  front  center  to  a 
transom  on  the  trail  in  such  a  manner  that  it  is  free  to  rotate  under 
control  of  the  traversing  gear.  4°  to  the  right  or  4°  to  the  left  of  the 
center  line  of  the  trail,  a  total  of  8°  traverse  for  each  of  the  three 
types. 


REAR  VIEW   OF  CARRIAGE,  SHOWING  MAXIMUM  ELEVATION  OF  HOWITZER. 

A  quick-loading  gear  is  fitted  to  the  cradle  for  bringing  the 
howitzer  rapidly  to  the  loading  position  (7°  30'  elevation)  after 
firing,  and  vice  versa. 

The  trail  is  composed  of  two  side  members  supported  at  the  front 
end  of  the  axle  and  terminating  in  a  spade  at  the  rear  end.  Screw 
brakes  for  use  in  firing  or  traveling  are  fitted  to  either  side  at  the  for- 
ward end  of  the  trail. 

A  traveling  lock  is  provided  on  the  trail  to  lock  the  trail  and 
cradle  together  to  prevent  strains  on  the  elevating  and  traversing 
mechanisms  when  traveling. 


285 

The  wheels  are  made  entirely  of  steel  and  have  wide  tires  fitted  with 
steel  cleats  to  ensure  good  traction. 

The  sighting  gear  is  composed  of  a  rocking  bar  sight  with  pano- 
ramic sight  and  clinometer  for  the  usual  method  of  sighting  and  a  dial 
sight  for  the  quick  laying  of  the  piece. 


SIDE   VIEW   OF   CARRIAGE   IN   BATTERY 


Comparative  table  of  weights  and  dimensions  of  8-inch  howitzer  carriages,  Marks 
VI  and  VII,  and  6-inch  gun  carnage,  Mark  VIII-A. 


Mark  VI. 

Mark  VII. 

MarkVIHA. 

Weight  of  carriage  only  
Weight  of  carriage,  limber,  and  howitzer  or  gun  

..pounds.. 
do  

12,548 
21,700 
29,540 
19,100 
528 
54.0 

12,320 
22,650 
30,490 
20,050 
532 
64.8 
1,700 
76.8 
740 
1,859 
•       60 
69 
95.8 
4°  right 
4"  left 
26°  right 
26°  left 
66 
12 
78 

276.5 
280 

12,548 
25,110 
32,950 
22,796 

Weight  behind  team,  heaviest  load  

...do... 

Weight  of  howitzer  or  gun  carriage  in  firing  position  

....do.... 

Weight  at  end  of  trial  

.  .do  .  . 

Volume  of  liquid  in  recoil  cylinder  
Volume  of  air  in  recuperator  cylinders  

.  ..pints.. 

nil.  in 

64.8 
'1,693 
~76.8 
740 
1,678 
I  60.  5 

Volume  of  liquid  in  recuperator  cylinders  pints  .  . 
Initial  pressure  pounds  per  sq.  in.. 

Maximum  ftir  pressure                                                                             Hn 

70.0 
685 
1,008 
60 
69 
95.8 
\     4°  right 
/        4°  left 
\  26°  right 
/      26°  left 
66 
12 
76 

256.5 
260 

Height  of  bore*  above  ground  
Height  of  sight  line,  panoramic  sight  

..inches.. 
....do  .  . 

Width  of  carriage  over  axle... 

do 

95.8 
4°  right 
4°  left 
26"  right 
.     26"  left 
66 
12 
76 

322.5 
325 

Angle  of  traverse  
Angle  of  traverse  with  firing  platform  

.degrees.. 
....do  

Diameter  of  wheels  

inches 

Width  of  tires,  carriage  

.    ..do 

Width  of  track,  center  line  to  center  line  of  wheels  

.    .do.. 

Maximum  length  of  carriage,  firing  position  (howitzer  or  gun  hori- 
zontal)                        .       inches 

Maximum  length  of  carriage,  traveling  position  (howitzer  or  gun 
horizontal)  inrhps 

The  carriage  limber  is  made  of  steel  and  has  wide  steel-tired  wheels, 
At  the  rear  is  a  limber  hook  which  engages  the  lunette  at  the  trail 
end  of  the  carriage.  A  chest  is  mounted  on  the  limber,  providing 
seats  for  the  personnel,  and  fittings  on  the  interior  for  carrying  tools. 

The  limbers  which  were  manufactured  in  England  have  wooden 
chests,  while  those  manufactured  in  America  have  steel  chests.  A 
connecting  pole  provides  for  motor  transportation  when  traveling, 
the  units  being  arranged  in  the  following  order:  Limber,  gun  or 
howitzer  carriage,  and  platform  wagon,  which  combination  is  drawn 
by  a  tractor 


286 

These  types  of  carriages  are  provided  with  a  platform  by  means  of 
which  a  traverse  of  26°  right  and  26°  left  is  obtainable.  The  plat- 
form is  used  whenever  conditions  and  time  permit  emplacement. 
For  transportation  the  platform  is  disassembled  and  placed  on  a 
transport  wagon,  which  consists  of  two  wheels  and  an  axle,  to  which 
the  parts  of  the  platform  are  securely  clamped. 
Eight-inch  howitzer  materiel  (British)  consists  of: 

Model  of  1917  (Vickers,  Mark  VI  and  Mark  VII). 
Model  of  1918  (Vickers,  Mark  VII). 
Limber,  model  of  1917  (Vickers). 
Firing  platform  and  wagon,  model  of  1917  (Vickers). 
The  8-inch  howitzer  materiel,  model  of  1917  (Vickers,  Mark  VI). 
consists  of : 

Carriage,  model  of  1917  (Vickers,  Mark  VI). 
Howitzer,  model  of  1917  (Vickers,  Mark  VI). 
Limber,  model  of  1917  (Vickers). 

Firing  platform  and  wagon,  model  of  1917  (Vickers). 
The  8-inch  howitzer  materiel,  model  of  1918  (Vickers,  Mark  VIII), 
consists  of : 

Carriage,  model  of  1918  (Vickers,  Mark  VII). 

Howitzer,  model  of  1918  (modified  from  Vickers,  Mark  VIII 

to  United  States,  Mark  VIIL}). 
Limber,  model  of  1917  (Vickers). 
Firing  platform  and  wagon,  model  of  1917  (Vickers). 
The  above  materiel  is  of  British  design  and  of  both  British  and 
American  manufacture. 


287 


55160—21 19 


8-INCH  HOWITZER  AND  CARRIAGE  (BRITISH). 


The  Mark  VI  howitzer  is  of  the  built-up-construction  type  and 
consists  of  a  tube  over  which  is  shrunk  a  jacket.  Front  and  rear 
guide  rings  provide  means  of  supporting  the  howitzer  in  the  cradle. 
A  breech  ring  is  also  shrunk  on  for  additional  strength  and  carries  a 
lug  for  connecting  the  gun  to  the  recoil  mechanism,  and  a  breech 
bushing  is  provided  for  reception  of  the  breechblock.  The  total 
length  of  this  howitzer  is  about  10|  feet  and  its  maximum  range  is 
approximately  10,760  yards:  this  howitzer  is  mounted  on  the  Mark 
VI  carriage. 


REAR  RIGHT  SIDE  OF  CARRIAGE   IN   FIRING  POSITION. 

The  Mark  Vlll\  howitzer  is  also  of  the  built-up-construction  type, 
but  differs  from  the  Mark  VI  howitzer  in  that  it  consists  of  two  tubes. 
an  inner  and  an  outer,  over  which  is  shrunk  the  jacket.  The  jacket 
in  this  case  supports  the  howitzer  without  the  use  of  guide  rings.  A 
breech  ring  is  shrunk  on  over  the  jacket  and  carries  a  lug  for  connect- 
ing the  gun  to  the  recoil  mechanism.  A  breech  bushing  similar  to 
that  of  the  Mark  VI  is  fitted  for  the  breech  mechanism.  The  total 
length  of  this  howitzer  is  about  12|  feet  and  its  maximum  range  is 
approximately  12.360  yards.  This  howitzer  is  mounted  on  the  Mark 
VII  carriage. 

(288) 


289 


290 


291 

The  breechblock  is  of  the  interrupted-screw  type.  It  is  operated 
by  a  lever  on  the  right-hand  side  of  the  breech,  which  by  one  motion 
releases  the  screw  threads  and  opens  the  breech,  or  vice  versa,  on 
closing. 

The  forward  mushroom-shaped  head  of  the  breechblock  is  equipped 
with  a  flexible  asbestos  ring,  known  as  the  obturator  pad.  On  firing, 
this  ring  is  compressed  and  acts  as  a  gas  check  to  prevent  the  leakage 
of  powder  gases  back  through  the  breech.  It  has  sufficient  resiliency 
to  resume  its  original  form  after  firing,  as  described  on  page  236. 

For  firing  the  charge,  two  separate  types  of  igniters  or  primers  are 
used.  The  one  known  as  the  T  tube  consists  of  a  small  T-shaped 
copper  tube  which  fits  into  a  suitable  socket  in  the  breech ;  it  is  fired 
by  pulling  a  friction  wire  out  of  the  tube  by  means  of  a  lanyard. 


BREECH    BLOCK. 

The  other  type,  the  percussion  primer,  is  very  similar  in  construc- 
tion to  a  blank  rifle  cartridge.  It  fits  a  percussion  firing  mechanism 
on  the  breech  which  fires  the  primer  by  means  of  a  hammer  operated 
by  the  lanyard.  This  mechanism  is  common  and  interchangeable 
with  the  155-millimeter  gun  and  howitzer;  also  the  240-millimeter 
howitzer. 

Howitzers  fitted  for  one  type  of  primer  will  not  permit  the  use  of 
the  other  type.  Both  types  have  a  safety  lock,  which  prevents  firing 
when  the  breech  is  not  entirely  closed. 

The  recoil  mechanism  is  of  the  hydropneumatic  long-recoil  type 
and  contains  both  recoil  brake  and  recuperator. 

The  recoil  mechanism  is  an  hydraulic  brake  to  absorb  the  energy  of 
recoil  of  the  piece.  It  consists  of  a  piston  rod  and  piston  traveling 
in  an  oil-filled  cylinder.  The  piston  rod  is  connected  to  the  cradle. 


292 


o 


CD 


293 

which  remains  stationary  while  the  howitzer  recoils.  The  cylinder 
block  is  connected  to  a  lug  on  the  howitzer  and  recoils  with  it  so  that 
when  the  gun  is  fired  the  piston  is  forced  against  the  oil  in  the  cyl- 
inder. Ports  are  provided  in  the  piston  to  permit  of  the  passage  of 
some  of  the  oil.  At  the  beginning  of  the  recoil  a  large  quantity  of 
oil  is  permitted  to  pass,  but  as  the  howitzer  further  recoils  a  valve 
on  the  piston  rod,  operated  by  lugs  sliding  in  spiral  grooves  in  the 
cylinder  walls,  gradually  closes  the  port  so  that  no  oil  can  pass  and 
the  howitzer  is  brought  gradually  to  rest. 


FRONT   VIEW   OF   HOWITZER   CARRIAGE. 

In  order  to  prevent  the  gun  striking  the  ground  when  firing  at 
high  elevation,  a  method  is  provided  for  automatically  closing  the 
piston  valves  sooner  as  the  elevation  increases,  thus  shortening  the 
recoil.  The  mechanism  which  accomplishes  this  feature  is  known 
as  the  valve  turning  gear. 

The  rear  end  of  the  piston  rod  is  extended  and  so  designed  that  it 
forms  a  counterrecoil  buffer  when  it  enters  a  suitable  chamber  bored 
out  in  the  buffer  plug.  This  buffer  prevents  violent  return  into 
firing  position  after  recoil. 

The  recuperator  or  counterrecoil  mechanism  serves  to  return  the 
howitzer  to  firing  position  after  recoil.  It  consists  of  two  liquid 


294 

cylinders  which  are  connected  in  turn  with  two  air  cylinders.  On 
recoiling,  the  recuperator  pistons  force  the  oil  out  of  the  recuperator 
cylinders  into  the  air  cylinders,  thereby  highly  compressing  the  air. 
When  this  air  expands  to  its  original  volume  it  drives  the  oil  back 
against  the  recuperator  pistons,  thereby  returning  the  howitzer  to 
firing  position.  The  recuperator  also  acts  as  an  auxiliary  recoil 
buffer,  absorbing  about  10  per  cent  of  the  energy  of  recoil.  The 
air  in  the  recuperator  is  maintained  at  a  pressure  of  about  700  pounds 
per  square  inch  in  order  to  prevent  the  howitzer  slipping  back  on  the 
cradle  at  high  elevations.  A  suitable  pump  is  provided  with  the 
material  for  maintaining  this  air  pressure. 


ELEVATING   AND   TRAVERSING   MECHANISM. 

The  carriage  consists  of  a  top  carriage,  cradle,  trail,  wheels  with 
axles,  and  the  elevating  and  traversing  gear.  The  Mark  VI  and 
Mark  VII  carriage  are  similar  in  design  and  differ  only  in  that  Mark 
VII  has  a  slightly  larger  recoil  mechanism  and  the  trail  is  cut  out 
somewhat  to  allow  for  the  greater  length  of  the  howitzer  recoil. 

The  top  carriage  is  built  up  of  nickel-steel  plate  and  carries  the 
trunnion  bearings  for  the  cradle.  It  is  pivoted  in  the  front  transom 
of  the  trail,  so  as  to  permit  the  necessary  traverse. 

The  cradle  which  carries  the  recoil  mechanism  and  provides  slide 
ways  for  the  recoil  of  the  howitzer  when  in  action  is  supported  by 
the  trunnion  bearings  of  the  top  carriage. 


295 


296 


297 

The  trail  is  of  the  solid  type,  cut  out  to  provide  clearance  for  the 
howitzer  to  recoil.  The  spade  is  removable  and  the  shoe  or  bracket 
may  be  substituted  when  firing  on  scotches  or  using  the  firing  plat- 
form. 

The  elevating  and  traversing  gears  are  operated  by  handwheels  on 
the  left  side  of  the  carriage.  The  Mark  VI  carriage  permits  of  an 
elevation  of  50°;  the  Mark  VII,  45°;  and  the  Mark  VIIIA,  38°. 
All  three  carriages  permit  a  traverse  of  8°. 

A  quick-loading  gear  is  provided  to  allow  the  gun  to  be  brought 
rapidly  to  loading  position  when  firing  at  high  angles  of  elevation. 

The  wheels  are  of  the  all  steel  wide-tire  type,  66  inches  in  diameter 
with  tires  12  inches  wide.  They  are  fitted  with  brakes  which  act 
independently  on  each  wheel. 

Sighting  is  accomplished  by  means  of  a  rocking-bar  sight  supple- 
mented by  a  panoramic  sight.  These  are  located  on  the  left  side  of 
the  piece  and  serve  to  lay  for  elevation  and  traverse  respectively. 
A  dial  sight  is  provided  on  the  right  side  of  the  piece  for  quick 
laying. 

Ammunition  of  the  separate  loading  type  is  used  with  the  8-inch 
howitzer.  Shell  issued  is  of  the  high-explosive  type  only  and  weighs 
200  pounds.  These  are  issued  filled  but  not  fuzed  and  are  fitted  with 
a  booster  and  adapter.  Fuzes  of  types  to  suit  different  conditions 
of  firing  are  provided,  giving  delayed  or  instantaneous  action. 

The  propelling  charge  is  contained  in  cloth  bags  and  is  made  up  of 
separable  increments,  permitting  various  zones  of  fire.  The  maxi- 
mum charge  for  the  Mark  VI  howitzer  weighs  10.8  pounds ;  for  the 
Mark  VIII£  howitzer.  17.5  pounds. 

Separate  loading  ammunition  is  used  in  the  6-inch  gun  mounted 
on  a  Mark  VIIIA  carriage.  The  original  British  ammunition  so 
closely  resembled  the  American  that  it  was  decided  to  use  the  regular 
Mark  II  high-explosive  shell.  Each  round  is  issued  with  the  projec- 
tile filled,  also  the  adapter  and  booster  in  place.  The  fuze  hole  in 
the  adapter  is  fitted  with  a  white-metal  plug.  The  weight  of  the 
projectile  complete  is  90.33  pounds.  The  propellant  charge  will 
consist  of  a  base  section  and  increment  section  having  a  total  weight 
of  approximately  25  pounds. 


298 

CATERPILLAR  ADAPTERS. 

The  application  of  the  adapter  to  this  weapon  requires  a  slight 
alteration  in  the  wheeled  carriage;  i.  e.,  wheels  and  adapters  are 
not  entirely  interchangeable.  The  unit  ground  pressure  of  this 


CATERPILLAR   ADAPTERS   FOR   8-INCH   HOWITZER   CARRIAGE,   MARK    VI   AND    VII. 

weapon  on  the  wheeled  carriage  is  32  pounds  per  square  inch.  By 
using  the  adapter  this  is  reduced  to  12  pounds,  with  the  correspond- 
ing increase  in  mobility.  In  addition  to  the  experimental  adapters 
on  hand,  sufficient  are  being  constructed  to  equip  the  howitzers  of 
two  batteries,  in  accordance  with  recommendation  of  the  Artillery 
Equipment  Board,  for  more  extended  service  test. 


8-INCH  HOWITZER  CARRIAGE  LIMBER,  MODEL  OF  1917 

(VICKERS). 


The  limber  provided  with  this  and  for  the  6-inch  gun  materiel  is 
of  steel  construction  and  provides  a  chest  for  tools  and  spares,  also 
seats  for  the  personnel.  No  ammunition  is  carried  in  this  limber, 
but  two  types  of  poles  are  provided,  a  long  one  for  horse-drawn 
vehicles  and  a  shorter  connecting  pole  for  motor  traction. 

The  box  or  chest,  of  limbers  manufactured  in  England,  is  of  wood 
and  is  bolted  to  the  top  of  the  rails.  The  lid  is  covered  with  water- 
proofed canvas  and  hinged  at  the  front.  Those  limbers  which  were 
manufactured  in  the  United  States  are  provided  with  steel  chests 
which  vary  slightly  from  the  wooden  chests  in  fittings  provided  for 
tools  and  accessories. 

The  axle  is  cylindrical  in  shape  and  fitted  with  special  axle  arms. 
It  passes  through  bearings  formed  in  the  rails  and  is  held  in  position 
by  brackets. 

The  top  of  the  chest  is  equipped  with  guard  irons  and  blanket 
straps,  receptacles  being  provided  on  the  sides  and  ends  to  take  an 
ax,  a  shovel,  and  other  implements.  The  interior  of  the  chest  is 
fitted  to  carry  tools,  spare  packings  for  buffer  and  recuperator,  and 
other  necessary  stores.  Clips  are  secured  at  the  front  of  the  chest 
to  accommodate  two  rifles,  used  in  emergencies  when  attacked  en 
route. 

The  wheels  are  66  inches  in  diameter  and  have  a  tire  6  inches  in 
width  with  rounded  edges. 

Weights  and  dimensions. 

Length  of  wheel  base,  limber,  and  carriage  (limbered) inches 187 

Overall  length  of  limber,  carriage,  and  firing  platform  wagon   (tractor 

draft) inches 550 

Turning  angle degrees 40 

Weight  of  limber,  empty pounds—  2, 160 

Weight  of  limber,  fully  equipped  and  loaded do 2, 600 

Diameter  of  wheels inches—        66 

Width  of  tires do 6 

Width  of  track do 82 

Weight  of  each  wheel pounds 554 

Number  of  men  carried 3 

(299) 


300 


8-INCH  HOWITZER  FIRING  PLATFORM  AND  WAGON, 
MODEL  OF  1917  (VICKERS). 


A  wooden  firing  platform  is  provided  on  which  the  carriage  of 
the  8-inch  howitzer  and  6-inch  gun  materiel  can  be  mounted  when 
sufficient  time  is  permitted  for  setting  up.  The  platform  consists 
of  wooden  beams  which  assemble  to  form  a  triangular  platform. 
The  spade  must  be  removed  and  a  special  bracket  fitted  on  the  trail 
when  using  this  platform.  This  bracket  travels  in  a  groove  which 
gives  a  bearing  for  the  bracket  and  also  provides  a  means  of  travers- 
ing the  piece  52°  on  the  platform.  The  platform  is  disassembled 
and  mounted  on  a  pair  of  wheels  and  axle  for  transportation. 

The  main  objects  in  the  use  of  the  firing  platform  are:  To  pro- 
vide a  reliable  support  for  the  wheels  and  rear  end  of  the  trail,  so 
as  to  prevent  sinking  or  movement  when  firing  on  soft  ground;  to 
insure  the  gun  remaining  on  the  target  when  firing ;  and  to  provide 
means  for  shifting  the  trail  transversely  through  an  angle  52° 
(26°  each  .side  of  center).  By  using  the  traversing  gear  on  the  car- 
riage a  total  traverse  of  30°  on  each  side  of  the  center  is  obtainable. 

The  firing  platform  is  composed  of  a  support  upon  which  the 
wheels  of  the  carriage  rest,  two  side  beams  hinged  together  at  the 
forward  end  and  a  rear  beam  made  in  a  top  and  bottom  section. 
These  components  form  a  triangular-shaped  frame  upon  which  the 
carriage  may  be  placed  when  firing. 

The  support  for  the  carriage  wheels  is  placed  near  the  apex  of  the 
triangle  formed  by  the  hinged  side  and  rear  beams.  The  rear  beams 
form  the  base,  the  upper  one  being  curved  at  its  front  edge  to  form 
a  guide  for  shifting  the  trail.  The  carriage  wheels  rest  on  steel 
plates  on  the  wheel  platform  and  are  guided  by  curved-steel  angles 
which  prevent  lateral  movement  of  the  gun  off  the  target  when  in 
action. 

When  the  firing  platform  is  used,  the  float  plate,  with  spade  at- 
tached, which  is  bolted  to  the  underside  of  the  trail,  is  removed  and 
another  float  plate,  having  a  thrust  bracket  attached,  is  bolted  in 
its  place. 

In  traveling  the  units  of  the  8-inch  materiel  are  arranged  in  the 
following  order :  Limber,  carriage,  and  platform  wagon.  The  usual 
plan  is  to  draw  this  combination  by  a  tractor. 

(301) 


302 


303 

Weights  and  dimensions. 

Overall  length  of  wagon  (traveling  position) inches 240 

Overall  height  of  wagon do 66 

Overall  width  of  wagon '. do 105 

Diameter  of  wheels do 66 

Width  of  tires do 6 

Width  of  track do 85 

Road  clearance do 18 

Weight   of  platform pounds 5,  740 

Weight  of  wood  platform  and  wagon  (complete) do 7,840 

Weight  of  steel  platform  and  wagon  (complete) do 9,630 

55160—21 20 


304 


VIEWS  SHOWING  9.2-INCH  HOWITZER  CARRIAGE  (MARK  II)  IN  BATTERY  POSITION. 


305 

9.2-INCH  HOWITZER  MATERIEL  (VICKERS). 

The  9.2-inch  and  240-millimeter  howitzers  are  the  largest  weapons 
of  the  mobile  type  in  service  witli  the  American  Army  at  the  present 
time.  While  these  calibers  are  mobile  in  a  sense,  yet  there  are  limits 
to  their  mobility,  for  when  they  have  to  be  transported  over  land 
full  of  huge  craters,  with  the  roads  entirely  destroyed,  the  country 
encumbered  with  all  kinds  of  debris,  and  frequently  reduced  to  a  sea 
of  mud,  one  can  realize  just  why  a  successful  attack  usually  nets 
captured  artillery,  and  on  the  other  hand,  if  the  trenches  give  way, 
it  is  very  difficult  to  get  these  heavy  howitzers  away  quickly  enough 
to  save  them  from  being  captured  by  the  enemy. 

Both  types  of  9.2-inch  howitzers  are  practically  similar  in  all 
features,  both  being  platform  mounts  as  illustrated.  These  units 
break  up  into  three  separate  loads  for  traveling,  the  howitzer  proper 
forming  one  load,  the  top  carriage  and  cradle  the  second  load,  and 
the  platform  the  third  load. 

The  Mark  I  type  of  howitzer  is  13  calibers  long,  while  the  Mark  II 
type  is  17.3  calibers,  the  principal  difference  being  that  the  latter 
model  is  a  more  powerful  weapon.  Both  types  are  provided  with 
an  earth  box  which  is  secured  on  firing  beams,  and  in  which  the  earth 
excavated  for  the  firing  beams  is  thrown ;  the  additional  weight  gives 
greater  stability  when  firing. 

The  recoil  mechanism  is  of  the  variable  type  which  limits  the 
amount  of  recoil  according  to  the  elevation,  the  recoil  cylinder  being 
fitted  with  a  counterrecoil  buffer  to  control  the  return  of  the  howitzer 
into  battery.  A  gravity  tank  insures  that  the  recoil  cylinder  will 
at  all  times  be  filled  with  the  proper  amount  of  oil  and  provided 
with  the  necessary  amount  of  void  for  the  expansion  of  the  oil. 

The  counterrecoil  mechanism  is  of  the  hydropneumatic  type  con- 
sisting of  a  cylinder,  ram,  and  floating  piston  with  rod.  The  floating 
piston  forms  a  barrier  between  the  air  and  oil  to  prevent  aeration 
and  to  form  an  intensifier  to  prevent  leakage  of  air  by  opposing  a 
superior  pressure  of  liquid  to  it. 

In  the  operation  of  firing  the  howitzer  the  recoil  cylinder  and 
the  counterrecoil,  or  recuperator  piston  rod,  move  to  the  rear  with 
the  howitzer,  the  recoil  piston  rod  and  the  recuperator  cylinder 
remaining  stationary.  The  flow  of  oil  in  the  recoil  cylinder  past 
the  piston  rod  and  valve  limits  the  length  of  the  recoil  and  the  com- 
pression of  the  air  in  the  recuperator  cylinder  is  sufficient  to  return 
it  to  battery  after  the  force  of  the  recoil  has  been  absorbed.  The 
counterrecoil  buffer  in  the  recoil  cylinder  limits  the  counterrecoil  of 
the  howitzer  and  allows  the  piece  to  return  to  battery  position  with- 
out shock. 


306 


307 

The  howitzer,  being  comparatively  thick  and  short  when  com- 
pared with  a  gun  of  the  same  caliber,  is  capable  of  greater  angle  of 
elevation  than  the  same  caliber  of  gun.  The  gun  is  primarily  in- 
tended for  attacking  troops  while  the  chief  aim  of  the  howitzer  is  to 
destroy  incumbrance  such  as  trenches,  barbed  wire,  pill  boxes,  and 
the  like.  A  shell  that  travels  from  the  howitzer  ascends  at  a  high 


FRONT  VIEW  SHOWING  MAXIMUM  ELEVATION   OF  HOWITZER. 

angle  and  drops  almost  vertically.  The  explosion  of  a  shell  so  fired 
is  much  more  effective  than  one  that  is  fired  with  only  a  slight  ele- 
vated trajectory  as  in  the  case  of  the  field  gun  of  the  same  caliber. 
From  information  based  on  actual  experience,  the  9.2-inch  how- 
itzer, Mark  I  type  (low  velocity),  has  an  average  life  of  8,300  rounds, 
while  the  Mark  II  (high  velocity)  has  an  average  life  of  3,500  rounds. 


308 

The  howitzer  transport  wagon  is  a  four-wheeled  vehicle  the  body 
of  which  contains  a  winch  for  removing  and  mounting  the  howitzer 
in  the  cradle.  This  vehicle  is  equipped  for  motor  traction  and  has 
brakes  acting  individually  on  each  hind  wheel. 

The  carriage  bed  (or  platform)  transport  wagon  is  formed  by 
fixing  a  front  and  rear  axle  to  suitable  attachments  on  the  bed,  thus 
forming  the  body  of  the  wagon.  Attachments  are  provided  for 
brakes  which  act  independently  on  each  hind  wheel  and  connections 
for  attachment  behind  the  howitzer  transport  wagon. 


LOADING  POSITION    OF   HOWITZER,   SHOWING   SHELL   ON   TRAY. 

The  top  carriage  transport  wagon  is  formed  by  attaching  two 
axles  with  wheels  to  the  top  carriage,  which  forms  the  body.  Indi- 
vidual brakes  are  fitted  on  the  hind  wheels.  This  vehicle  is  usually 
coupled  behind  the  platform  wagon. 

The  three  wagons  are  drawn  en  train  by  tractor  but  may  be  hauled 
singly  in  case  of  necessity. 

The  9.2-inch  howitzer  materiel  (Vickers),  Mark  I  consists  of: 
Howitzer  carriage,  model  of  1917. 
Howitzer  platform  transport  wagon,  model  of  1917. 
Howitzer  carriage  transport  wagon,  model  of  1917. 
Howitzer  transport  wagon,  model  of  1917. 

The  9.2-inch  howitzer  materiel  (Vickers),  Mark  II,  consists  of: 
Howitzer  carriage,  model  of  1918. 
Howitzer  platform  transport  wagon,  model  of  1918. 
Howitzer  carriage  transport  wagon,  model  of  1918. 
Howitzer  transport  wagon,  model  of  1918. 


309 


9.2-INCH  HOWITZERS  AND  CARRIAGES,  MARKS  I  AND  II 

(BRITISH). 


This  materiel  is  designed  to  be  transported  in  separate  loads,  thus 
three  four-wheeled  vehicles  are  issued  for  this  purpose.  The  first 
carries  the  howitzer,  the  second  the  carriage,  and  the  third  the  plat- 
form and  earth  box,  all  of  which  is  of  British  design,  but  the  United 
States  is  in  possession  of  equipment  made  both  in  this  country  and 
in  Great  Britain. 


REAR   VIEW    OF   CARRIAGE,    SHOWING    HOWITZER    AT    MAXIMUM    ELEVATION. 

The  howitzer  consists  of  a  tube,  muzzle  stop  ring,  a  series  of  layers 
of  steel  wire,  jacket,  breech  bushing,  and  breech  ring.  Over  the 
exterior  of  the  tube  is  wound  a  series  of  layers  of  steel  wire  extending 
from  the  breech  end  to  the  stop  ring,  which  is  shrunk  over  the  tube 
at  the  muzzle.  Over  the  exterior  of  the  tube  is  shrunk  the  jacket, 
which  is  secured  longitudinally  by  the  breech  bushing.  The  bushing 
is  prepared  for  the  reception  of  the  breechblock.  The  breech  ring  is 
screwed  and  shrunk  over  the  jacket  at  the  rear. 

(310) 


311 

The  Mark  II  differs  in  that  it  has  two  tubes  shrunk  one  over  the 
other  on  which  the  wire  is  wound.  The  Mark  I  howitzer  is  133£ 
inches  in  length,  while  the  Mark  II  is  170£  inches. 

The  breech  mechanism  of  the  screw  type  with  plastic  obturator  is 
so  arranged  that  by  partially  revolving  the  operating  lever  the 
breechblock  is  unlocked  and  the  block  with  the  gas-check  pads  and 
disks  withdrawn  from  the  seating  in  the  chamber.  The  breech  mech- 
anism can  then  be  swung  into  the  loading  position  by  means  of  a 
handle  on  the  rear  face  of  the  breechblock.  The  breech  is  closed  by  a 
parallel  screw  having  five  portions  of  the  screw  thread  removed  longi- 
tudinally, each  one-tenth  of  the  circumference.  The  main  character- 
istics of  the  Vickers  9.2-inch  howitzers  are  indicated  in  the  accom- 
panying table,  giving  the  important  dimensions,  weights,  and  ballistics. 

The  Mark  I  breech  requires  two  operations  to  open.  A  handle 
turning  on  the  rear  of  the  block  revolves  and  releases  the  block,  then 


BREECH  MECHANISM    (MARK  I). 

it  must  be  swung  open  by  the  handle  provided  on  the  breech.  The 
Mark  II  breech  can  be  opened  by  one  motion  of  a  lever  on  the  right 
side  of  the  breech,  which  revolves  and  withdraws  the  breech  in  one 
motion  from  front  to  back. 

Both  types  are  fitted  with  a  firing  mechanism  to  accommodate  the 
T-tube  primer.  Later  models  are  fitted  with  the  French  percussion 
type  of  firing  mechanism  described  with  the  155-millimeter  howitzer 
materiel  on  page  236. 

The  recoil  mechanism  is  of  the  hydropneumatic  type  and  is  equipped 
with  a  variable  recoil,  which  shortens  the  length  of  recoil  after  15° 
elevation. 

The  recoil  cylinder,  located  above  the  howitzer  and  secured  thereto, 
moves  with  it,  while  the  piston  rod  is  secured  to  the  cradle  and  re- 
mains stationary.  The  recoil  is  controlled  by  passage  of  oil  through 
ports  in  the  cylinder,  which  are  varied  by  the  valve  located  near 


312 

the  piston  on  the  rod.  This  valve  is  rotated  by  lugs  which  en- 
gage spiral  grooves  in  the  cylinder.  A  mixture  of  glycerine  and  oil 
is  used  in  the  cylinder.  Later  models  are  fitted  with  gravity  tank 
on  top  of  the  recoil  cylinder  to  replenish  the  oil  and  relieve  pressure 
due  to  expansion.  The  end  of  the  piston  rod  is  extended  and  shaped 
to  form  a  counterrecoil  buffer. 

The  recuperator  is  located  below  the  howitzer.  The  cylinder  being 
secured  to  the  cradle  remains  stationary  when  the  howitzer  is  recoil- 
ing ;  but  the  ram  is  secured  to  the  howitzer  and  moves  with  it.  The 
oil  and  air  in  this  cylinder  are  separated  by  a  floating  piston.  The 
ram  on  recoiling  increases  the  liquid  pressure  on  this  piston ;  this  in 
turn  compresses  the  air,  which  on  expansion  will  return  the  howitzer 
to  battery.  An  initial  pressure  of  475  pounds  per  square  inch  is 
maintained  in  the  air  chamber  to  hold  the  piece  in  battery. 


ft/MCt  LU» 

RCTRIHINC  C/ITCH 


BREECH  MECHANISM    (MARK   II). 

To  maintain  this  pressure  a  pump  is  attached  to  the  carriage, 
which  can  be  operated  either  by  hand  or  a  small  gasoline  engine. 

The  cradle  is  a  cylindrical  casting  formed  to  house  the  howitzer. 
It  is  provided  with  trunnions  and  has  the  elevating  arc  secured  to  its 
lower  side.  Grooves  cut  in  the  cradle  cylinder  serve  to  guide  the 
howitzer  during  recoil.  A  toothed  arc  on  the  left  trunnion  operates 
the  valve  turning  gear  through  gearing. 

The  top  carriage  or  body  is  built  up  of  steel  plates.  A  front  tran- 
som carries  the  pivot  block,  which  fits  over  the  pintle  on  the  bed  and 
on  which  the  top  carriage  pivots.  To  the  rear  transom  is  secured  a 
pinion  which,  meshing  with  a  rack  on  the  bed,  serves  to  traverse  the 
piece.  Suitable  platforms  are  hinged  to  the  body,  thus  permitting 
access  to  working  parts  and  loading  platform  on  the  rear  for  the  per- 
sonnel. On  the  left  rear  side  of  the  body  is  a  loading  gear,  which 
consists  of  a  swinging  arm  with  a  winch  and  loading  tray. 


313 


314 

The  traversing  gear  is  actuated  by  a  hamlwheel  on  the  left  side  of 
the  carriage,  motion  being  transmitted  to  a  vertical  rack  pinion  which 
works  in  the  rack  at  the  rear  of  the  bed ;  thus  a  traverse  of  30°  right 
and  left  may  be  obtained. 


METHOD   OF    LOADING,   SHOWING    LOADING    GEAR   MECHANISM   IN   ACTION. 

The  elevating  gear  is  operated  by  a  handwheel  on  the  left  side  of 
the  carriage,  which,  through  a  system  of  gearing,  operates  the  arc 
beneath  the  cradle. 


RIGHT   SIDE   VIEW   OF   CARRIAGE   IN   BATTERY. 

A  quick-loading  gear  operated  by  a  handwheel  on  the  right  of  the 
carriage  permits  the  howitzer  to  be  brought  readily  to  the  loading 
angle.  3°  depression.  The  firing  angle  ranges  from  15°  elevation  to 
55°  elevation. 


315 


316 


317 


The  bed  on  which  the  top  carriage  pivots  consists  of  two  steel 
side  guides  of  box  section  with  transom,  a  pivot  block,  and  a  trav- 
ersing rack.  The  bearing  of  the  top  carriage  is  formed  by  an  upper 
and  lower  roller  path.  At  the  front  of  the  bed  are  suitable  connec- 
tions for  fastening  a  steel  box  which  is  filled  with  earth  to  help  main- 
tain stability. 

/Sighting  is  accomplished  by  means  of  a  rocking-bar  sight,  a  pano- 
ramic sight,  or  a  No.  7  dial  sight  located  on  the  left  of  the  carriage. 

The  rocking-bar  sight  serves  to  lay  for  elevation  and  carries  the 
telescope  sight  or  the  dial  sight  for  laying  for  direction.  The  dial 
sight  is  similar  to  the  United  States  panoramic  sight,  which  can  be 
substituted. 

Ammunition  employed  is  of  the  separate-loading  type.  High- 
explosive  steel  shell  weighing  290  pounds  are  used,  which  are  fitted 
with  percussion  fuses. 

The  propelling  charge  is  put  up  in  cloth  bags,  charges  built  up 
with  four  and  with  five  increments  for  zone  fire  being  provided. 
The  charge  is  ignited  by  the  T-tube  friction  type  of  primer. 

Weight,  dimensions,  and  ballistics. 


MarkL 


Mark  II. 


Weight  of  howitzer  without  breech  mechanism pounds.. 

Weight  of  howitzer  with  breech  mechanism do 

Total  length  of  howitzer inches . . 

Rifling  (uniform). 

Powder  charge pounds. . 

Weight  of  shell do.... 

Muzzle  velocity ft.  per  sec. . 

Maximum  range yards . . 

Weight  of  mount  in  firing  position  complete  with  howitzer  (but  without  dirt  in 

earth  box) pounds.. 

Weight  of  body  and  cradle do 

Weight  of  bed  and  earth  box do 

Weight  of  earth  box  empty do 

Weight  of  firing  beams do 

Weight  of  ground  ramps do 

Length  of  recoil  at  15*  elevation inches 

Length  of  recoil  at  50°  elevation do. . 

Maximum  angle  of  elevation degrees 

Loading  angle  (depression) do. . 

Amount  of  traverse do. . 


6,320 

6,800 

133J 

13f 

290 

1,187 

10,060 

29,100 

10,100 

8,200 

1,600 

4,200 

410 

40 

19 

50 

3 

60 


9,576 
170i 

27 

290 

1,500 

13,080 

35,500 

11,200 

9,100 

2,100 

5,700 

530 

44 

19 

50 

3 

60 


9.2-INCH  HOWITZER  TRANSPORT  WAGON  (VICKERS). 


This  wagon  consists  of  a  front  and  rear  axle  and  a  steel  rectangu- 
lar bed  prepared  for  transporting  the  howitzer. 

The  front  axle  is  of  forged  steel,  having  an  axle  arm  on  each  end, 
to  which  are  fitted  60  by  6-inch  steel  tired  wooden  wheels.  The 
steel  framework  is  formed  for  the  reception  of  the  axle  and  draft  pole, 
and  has  provisions  for  the  attachment  of  a  tractor. 

The  bed  for  transporting  the  howitzer  is  prepared  on  its  upper  sur- 
face to  receive  the  howitzer  and  is  supported  at  the  rear  on  an  axle, 
each  axle  arm  being  provided  with  a  dust  excluder  and  linch  pin. 
When  traveling  the  front  end  of  the  howitzer  is  secured  by  pawls, 
the  muzzle  end  being  supported  by  two  bronze  brackets  and  secured 


METHOD   OF  MOUNTING   HOWITZER. 

by  a  wire  rope  and  draw  nuts.  The  frame  is  fitted  with  a  draft 
link  in  rear  for  attachment  of  the  draft  connector  of  the  next  load. 

A  winch  gear  for  the  purpose  of  shifting  the  howitzer  into  or 
from  the  cradle  is  provided,  consisting  of  an  endless  chain  which, 
by  means  of  sprocket  wheels,  imparts  motion  to  a  larger  endless 
chain  to  which  the  howitzer  is  connected. 

Two  rods,  one  on  each  side,  are  secured  to  a  crossbar  for  connect- 
ing the  rear  of  the  wagon  to  the  carriage  body  when  mounting  or 
dismounting  the  howitzer. 

The  brake  gear  consists  of  two  brake  arms  and  brake  screw  fitted 
with  handwheels  and  two  brake  blocks.  Each  side  is  operated  inde- 
pendently by  handwheels  from  the  rear.  A  roller  scotch  and  drag 
shoe,  connected  by  chains,  are  attached  for  use  when  traveling. 

(318) 


319 

Weights  and  dimensions. 


Mark  I.       Mark  II. 

Overall  height  

inches 

84                      86 

Overall  width  

do  

96*                    109 

Weight  complete  with  load  

pounds  .  . 

10,600                14  700 

Weight  complete  without  load  

do... 

3,900                  5  200 

Weight  on  front  axle  (loaded)  

do  . 

5  700                  6  250 

Weight  on  rear  axle  (loaded)  

do  

4  900                  8*450 

Weight  of  each  wheel  

do  

336                    '336 

Width  of  track  

inches.  . 

82                      86 

Distance  between  axles  

do  ... 

88                      % 

Turning  angle  

degrees  .  . 

36                      37 

Turning  circle  diameter  

feet.. 

33                      35 

9.2-INCH  HOWITZER  CARRIAGE  TRANSPORT  WAGON 

(VICKERS) 

The  carriage  transport  wagon  consists  of  a  front  and  rear  axle, 
cross-bar,  brake  fittings,  draft  connection,  and  four  wheels. 

The  front  axle  is  of  forged  steel  equipped  with  arms  on  each  end 
and  to  which  are  fitted  the  wheels.  The  raising  screws  for  lifting  the 
carriage  into  position  function  through  two  vertical  holes  in  the 
axle. 

The  draft  frame  is  built  up  of  steel  plate  and  angles ;  is  triangular 
in  shape  and  formed  to  take  a  draft  pole  fitted  with  draft  hooks  for 
singletrees  also  joints  for  a  tractor  draft  connector.  The  draft  pole 
is  the  same  as  that  used  with  the  howitzer  transport  wagon. 

The  rear  axle  is  of  steel,  having  its  arms  cranked  and  fitted  with 
dust  excluders,  linch  pins,  and  adjusting  collars  which  are  secured  in 
position  when  traveling  by  the  blocks  and  pivot  on  the  front  of  the 
carriage  body.  These  fittings  allow  of  an  oscillation  which  com- 
pensates for  any  unevenness  in  ground. 

Brake  levers  for  each  of  the  brake  shoes,  on  each  side  of  the  vehicle, 
may  be  applied  independently.  The  mechanism  consists  of  brake 
screws,  handwheels,  brake  nuts,  and  bands  for  connection  to  the 
axle. 

The  roller  scotch  and  drag  shoe  furnished  are  the  same  as  those 
used  with  the  howitzer  transport  wagon. 

Weights  and  dimensions. 


Mark  I. 

Mark  II. 

inches.. 

103* 

Ill 

•Overall  width  

do.... 

Ml 

109 

Weight  complete  with  load                                .... 

pounds.  . 

12,600 

14.800 

Weight  complete  without  load  

do  

2.600 

3,600 

Weight  on  front  axle  (loaded)  

do.... 

5,000 

5,500 

Weight  on  rear  axle  (loaded)     .                         .  . 

...do... 

7,600 

9,300 

Weight  of  each  wheel  

do.... 

336 

336 

Width  of  track      

inches.. 

82 

86 

do.... 

115 

129 

degrees.  . 

32 

130  right. 

Turning  cicle,  diamete"      .  

feet.. 

34 

\86teft. 

25 

55160—21 21 


320 


321 

9.2-INCH    HOWITZER    PLATFORM   TRANSPORT   WAGON    (VICKERS). 

The  howitzer  platform  transport  wagon  in  general  is  very  similar 
to  the  howitzer  carriage  transport  wagon.  The  front  axle  and  draft 
connections  are  entirely  similar  to  those  on  the  howitzer  carriage 
transport  wagon,  except  that  only  one  hole  in  the  center  of  the  axle 
is  provided  for  the  raising  screw.  When  preparing  for  travel  the 
rear  axle,  which  is  fitted  with  two  vertical  holes  for  lifting  screws,  is 
attached  to  rear  of  the  bed.  The  axle  is  fitted  with  dust  excluder, 
linch  pins  and  adjusting  collars,  and  a  brake  gear  which  is  operated 
from  the  rear  by  handwheels,  each  side  being  operated  independ- 
ently. The  roller  scotch  and  drag  shoe  are  similar  to  those  used 
with  the  howitzer  carriage  transport  wagon. 

Weights  and  dimensions. 


Mark  I.       Mark  II. 

Overall  height  

inches  .  . 

65J                     60 

Overall  width  

do..  . 

%i                    109 

Weight  complete  with  load  

pounds.  . 

10,000                12,500 

Weight  complete  without  load  

...do... 

2,700                  3,500 

Weight  on  front  axle  (loaded)  

do.... 

4,900                  5,700 

Weight  on  rear  axle  (loaded)  

do  

6  000                  6  800 

Weight  of  each  wheel  

do  

336                     336 

Width  of  track  

inches.. 

82                       86 

Distance  between  axles  ... 

.  .do 

160                    174 

Turning  angle  

degrees 

40           f36  right. 

Turnine  circle,  diameter.  .  . 

...feet.. 

UOleft. 
48                      43 

322 


240-MILLIMETER  HOWITZER  MATfiRIEL,  MODEL  OF  1918 

(SCHNEIDER). 


The  240-millimeter  howitzer  unit,  a  French  design  modified  to 
accommodate  American  manufacturing  practice,  differs  from  the 
smaller  type  of  field  artillery  pieces  in  that  it  is  split  up  into  a  num- 
ber of  loads  for  transport.  When  arranged  for  firing  the  carriage 
is  set  upon  a  structural-steel  platform  which  rests  in  a  specially  pre- 
pared pit  and  has  a  large  trunk  portion  embedded  in  the  ground  to 
absorb  the  reaction  of  the  recoiling  parts.  The  platform  is  stabil- 
ized by  two  hinged  floats  at  the  rear. 


FRONT   VIEW  OF  CARRIAGE,  SHOWING  MAXIMUM   ELEVATION   OF   HOWITZER. 

Although  approximately  the  same  size  as  the  British  9.2-inch 
howitzer  (the  exact  diameter  of  the  bore  of  the  240  being  9.45  inches) 
and  only  a  little  larger  than  the  8-inch  howitzer,  the  French  gun  is 
by  far  more  powerful  than  either.  The  8-inch  and  9.2-inch  howitzers 
have  ranges  in  the  neighborhood  of  6  miles,  their  shell  weighing  200 
and  290  pounds,  respectively.  On  the  other  hand,  the  240  hurls  a 
shell  weighing  356  pounds  and  carrying  a  bursting  charge  of  45 
to  50  pounds  of  high  explosive,  obtaining  a  range  of  almost  10  miles. 
It  is  estimated  that  the  life  of  the  240-millimeter  howitzer  before 
relining  is  approximately  5.000  rounds. 

(323) 


324 


325 


Comparative  characteristics  of  heavy  artillery. 


8-inch  howitzer  carriage. 

9.2-inch  howitzer  carriage. 

240-millime- 
ter howitzer 
carriage. 

Mark  VI. 

Mark  VII. 

Mark  I. 

Mark  II. 

Weight  of  projectile,  pounds  

200 
1,300 
10,760 

29,540 
1 

19,100 
Hydropneu- 
matic. 
50-24 
s       0-50 
152 

200 
1,525 
12,600 

30,490 
1 

20,048 
Hydropneu- 
matic. 
52-24 
0-45 
152 

290 
1,187 
10,060 

10,640 
3 

16,240 
Hydropneu- 
matic. 
40-23 
15-50 
60 

290 
1,500 
13,080 

13,440 
3 

19,040 
Hydropneu- 
matic. 
44-19 
15^50 
60 

356 
1,700 
17,000 

14,000 
4 

37,920 
Hydropneu- 
matic. 
46.7 
-1-60 
20 

Muzzle  velocity,  feet  per  second  

Maximum  ranw,  yftms 

Weight  behind"  tractor  heaviest  load, 
pounds  

Number  of  loads  

Weight  of  carriage  and  gun  in  firing 
position,  pouring.  ,  . 

Typfl  of  rflWnl  mfi^hftnism.  ..    , 

Length  of  recoilj  inches  .  .  . 

Angles  of  elevation,  degrees  

Total  traverse,  degrees  

1  Traverse  when  firing  platform  is  used;  without  platform  a  traverse  of  8"  is  obtainable. 

In  firing  position  the  howitzer  proper  interlocks  and  becomes  inte- 
gral with  the  sleigh  containing  the  recoil  mechanism.  A  liquid  con- 
sisting of  glycerine  and  water  boiled  for  15  minutes  is  used  in  the 
recoil  cylinders  and  a  mixture  of  glycerine,  water,  and  caustic  soda 
is  used  in  the  recuperator. 

The  sleigh  has  two  bronze-lined  slideways  which  engage  the  clips 
on  the  cradle  so  that  the  sleigh  slides  upon  the  cradle  when  the  how- 
itzer recoils.  At  the  front  of  the  cradle  there  is  attached  a  cast-steel 
beam  to  which  the  piston  rods  of  the  recoil  and  recuperator  cylinders 
are  bolted.  The  cradle  also  carries  the  elevating  segments,  the  firing 
mechanism,  the  quick-return  mechanism,  and  a  trunnion  band  which 
supports  the  cradle  in  the  trunnion  bearings  of  the  top  carriage. 

The  top  carriage  is  composed  of  two. steel  flasks  united  by  cross 
transoms  and  end  plates,  and  at  the  rear  end  carries  the  brackets 
which  support  the  loading  platform  and  crane.  The  top  carriage  is 
pivoted  at  the  front  on  a  pintle  seat  supported  by  a  set  of  Belleville 
springs  in  a  pintle  socket  on  the  platform.  This  facilitates  traversing 
the  top  carriage  to  its  limits  of  10  degrees  either  to  the  right  or  left. 

The  howitzer  is  served  by  a  shot  truck  which  carries  two  356- 
pound  projectiles  and  runs  on  an  industrial  track  to  and  from  the 
ammunition  dump.  The  projectiles  are  lifted  from  the  shot  truck 
and  placed  on  a  rammer  car  by  shot  tongs  and  cable  operated  by  a 
hand  crane,  all  of  which  is  supported  by  a  loading  platform  at  the 
rear  of  the  top  carriage.  The  rammer  car,  operated  by  hand  cranks, 
moves  along  a  track  into  the  cradle,  registering  and  locking  with 
the  breech  of  the  howitzer,  after  which  the  projectile  is  pushed  into 
position  by  a  semiflexible  chain,  the  powder  charge  being  pushed  in 
by  hand. 

For  transportation  the  complete  howitzer  unit  is  divided  into  four 
loads,  namely,  howitzer,  cradle,  top  carriage,  and  platform.  Each 


326 

unit  is  composed  of  a  limber,  false  trail,  and  a  rear  two- wheeled  wagon. 
The  tools  and  accessories  for  each  unit  are  carried  on  two  4-ton  trail- 
ers and  the  six  loads  are  drawn  by  caterpillar  tractors. 

In  assembling  and  dismounting,  an  erecting  device  made  of  struc- 
tural steel  is  used  for  placing  the  platform  and  top  carriage  in  posi- 
tion. The  cradle  and  howitzer  are  drawn  into  place  by  a  cable  and 
windlass  which  is  attached  to  the  forward  part  of  the  top  carriage. 
This  erecting  device  is  also  used  for  lifting  and  placing  projectiles 
on  the  shot  truck  from  the  shell  storage. 

The  howitzer,  when  elevated  to  about  43^°  and  using  a  propelling 
charge  of  35  pounds,  giving  a  pressure  of  about  33,000  pounds  per 
square  inch  on  the  base  of  the  projectile,  will  fire  a  projectile  weigh- 
356  pounds  and  containing  a  bursting  charge  of  about  49  pounds 
of  T.  N.  T.  to  a  distance  of  approximately  10  miles. 


METHOD   OF   LOADING   THE   HOWITZER   WITH    RAMMER   CAR. 

The  following  sighting  equipment  is  carried  with  the  240-milli- 
meter materiel : 

Quadrant  sight,  model  of  1918. 

Panoramic  sight,  model  of  1917. 

Peep  sight. 

Sight  extension. 

Gunner's  quadrant,  model  of  1918. 

Night  lighting  equipment  for  sights. 

Ammunition  of  the  separate  loading  type  is  used  with  this  how- 
itzer, consisting  of  point- fuzed  high-explosive  common-steel  shell 
and  point-fuzed  gas  semisteel  shell.  The  shells  are  issued  filled  but 
not  fuzed,  the  fuze  hole  being  closed  with  a  suitable  plug.  The 
components  of  each  round  are  the  primer,  the  propelling  charge, 
the  filled  projectile,  and  the  fuzes. 

To  transport  the  complete  carriage,  there  are  provided  four  trans- 
port vehicles — howitzer  transport  wagon,  top  carriage  transport 
wagon,  platform  transport  wagon,  and  cradle  transport  wagon. 


327 


328 


329 

Each  transport  vehicle  consists  principally  of  a  limber,  false  trail, 
and  rear  axle  and  wheels. 

The  limber  consists  of  wheels,  axle,  pole,  and  turning  arc  and  is 
similar  for  each  wagon.  It  is  equipped  with  a  pintle,  over  which 
fits  the  lunette  ring  of  the  false  trail.  The  turning  arc  is  attached 
to  the  axle,  and  the  false  trail  bears  on  it  as  it  rotates  around  the 
pintle. 

Four  false  trails  are  provided,  one  for  each  wagon.  They  are 
fitted  at  the  front  end  with  a  lunette  ring  and  at  the  rear  with  a 
locking  arrangement  for  attachment  to  the  unit  to  be  transported. 

The  rear  axles  are  provided  with  suitable  means  for  attachment  to 
their  respective  units,  and  band  brakes  are  fitted  on  all  the  rear 
axles. 

When  the  complete  carriage  is  set  up  for  firing,  the  transport 
vehicles  are  close  coupled  by  means  of  the  false  trail  and  form  short 
units,  having  four  wheels,  which  can  be  drawn  away.  All  wheels 
are  equipped  with  solid  rubber  tires. 

ftlfi-mitllimeter  howitzer  materiel,  model  of  1918  (Schneider) ,  con- 
sists of : 

Howitzer  and  carriage,  model  of  1918. 
Howitzer  carriage  limber,  model  of  1918. 
Howitzer  transport  wagon,  model  of  1918. 
Howitzer  cradle  transport  wagon,  model  of  1918. 
Howitzer  top  carriage  transport  wagon,  model  of  1918. 
Howitzer  platform  transport  wagon,  model  of  1918. 
The  above  materiel  is  of  French  design,  but  was  manufactured 
only  in  the  United  States. 

240-MILLIMETER  HOWITZER  MODEL  1918  MI  AND  CARRIAGE, 
MODEL  OF  1918  (SCHNEIDER). 

The  howitzer  is  built  up  of  alloy  steel  and  consists  of  a  tube,  a 
jacket,  and  hoop.  The  jacket  is  shrunk  on  the  rear  end  of  the  tube 
and  is  secured  from  slippage  by  threads  cut  in  its  inner  surface, 
which  screw  over  corresponding  threads  on  the  tube,  the  rear  end 
of  which  is  prepared  for  the  reception  of  the  breechblock.  The 
hoop  is  shrunk  and  screwed  on  the  tube  forward  of  the  jacket,  which 
is  fitted  at  its  rear  end  with  a  hinge  lug,  vertical  clips  for  joining 
the  howitzer  to  the  sleigh,  and  guide  bosses  for  joining  the  sleigh  to 
the  howitzer ;  also  a  T-slot  to  suit  the  false  trail  when  en  train.  At 
the  front  end  of  the  hoop  is  a  boss  to  accommodate  the  axles  of  the 
transport  wagon,  and  lugs  for  rollers  used  in  the  dismounting  and 
mounting  of  the  howitzer. 

The  breech  mechanism  is  of  the  interrupted-screw  type  and  is 
fitted  with  a  plastic  obturator.  One  motion  of  the  breech  lever 
swinging  from  left  to  right  turns  and  swings  the  breech  clear. 


330 

The  firing  mechanism  is  of  the  French  percussion  type,  the  same 
as  used  on  the  155-millimeter  howitzer,  and  is  interchangeable  with 
the  mechanism  of  the  following  materiel : 

155-millimeter  gun,  model  of  1918  (Filloux). 
155-millimeter  howitzer,  model  of  1918  (Schneider). 
8-inch  howitzer,  Marks  VI  and  VIIIJ  (Vickers). 

The  sleigh,  a  steel  forging,  is  bored  out  to  house  the  recoil  mech- 
anism and  supports  the  howitzer,  being  attached  to  it  by  lugs  and 
locking  clips,  and  therefore  recoils  with  the  howitzer  when  in  action. 
Grooves  in  the  sleigh  house  guides  are  fastened  to  the  cradle,  which 
serve  to  guide  the  howitzer  in  recoil.  The  sleigh  is  also  fitted  with 
two  tracks  for  the  rollers  on  the  howitzer,  which  are  used  in  mounting 
and  dismounting. 

The  cradle  carries  the  trunnions  and  is  a  nonrecoiling  part.  The 
recuperator  piston  rod  and  the  recoil  piston  rods  are  attached  to  it. 


MOUNTING   THE   CRADLE. 

The  recoil  mechanism  is  of  the  hydropneumatic,  long-recoil  type, 
the  length  of  recoil  being  constant  for  all  elevations.  In  the  sleigh 
forging  are  bored  five  longitudinal  cylinders,  the  upper  two  being 
bored  about  half  the  length  of  the  sleigh  and  are  closed  at  the  front 
end  by  caps,  forming  air  reservoirs.  The  left  reservoir  has  an  open- 
ing in  which  the  pressure  gage  is  fitted  to  test  the  pressure  of  air  or 
gas. 

The  lower  cylinders  extend  the  full  length  of  the  sleigh,  while  the 
two  outer  cylinders  form  the  recoil  and  the  middle  the  recuperator 
cylinder.  The  recuperator  cylinder  is  connected  by  passages  to  the 
two  air  chambers,  permitting  the  liquid  from  the  recuperator  to  flow 
into  them. 

The  recoil  piston  rods  are  hollow  and  are  fixed  rigidly  to  the 
cradle.  In  the  hollow  space  travel  the  throttling  rods,  which  move 
with  the  recoiling  parts.  These  rods  are  so  shaped  that  they  give 
a  throttling  effect  on  the  liquid  which  passes  through  annular  open- 
ings around  the  piston.  On  return  to  battery  the  throttling  rods  act 
as  a  buffer  to  prevent  violent  return  into  battery. 


331 


332 


333 

The  air  (or  nitrogen  gas)  in  the  recuperator  is  maintained  at  a 
pressure  of  568  pounds  per  square  inch,  which  is  sufficient  to  keep 
the  howitzer  in  battery  at  all  elevations.  Tanks  of  compressed  nitro- 
gen are  kept  at  hand  to  replenish  that  in  the  recuperator  in  case  the 
pressure  gets  low.  The  liquid  used  in  both  recuperators  and  recoil 
cylinders  is  a  mixture  of  glycerin,  water,  and  caustic  soda.  Suitable 
pumps  are  provided  for  filling  these  cylinders. 

A  firing  handle  is  fitted  on  the  left  side  of  the  cradle,  which, 
through  a  system  of  shafts,  operates  the  percussion  hammer  on  the 
breech,  the  firing  handle  being  accessible  at  all  elevations  of  the 
howitzer.  In  case  of  emergency  the  piece  may  be  fired  by  means  of 
a  lanyard. 

The  elevating  mechanism  consisting  of  elevating  arcs,  which  tip  the 
cradle,  is  operated  by  a  handwheel  on  the  left  side  of  the  carriage 


LOWERING  THE  TOP  CARRIAGE  IN  POSITION. 

through  a  system  of  gearing.  A  maximum  elevation  of  60°  can  be 
obtained. 

In  connection  with  the  elevating  gear  a  quick-loading  gear  is 
provided,  by  means  of  which  the  howitzer  can  be  quickly  brought 
to  the  loading  angle  (9°  15')  and  again  elevated  without  the  use  of 
the  slower  method  of  using  the  elevating  gear.  A  handwheel  on  the 
right  side  of  the  carriage  is  used  to  operate  the  quick-loading  gear. 

The  top  carriage  is  a  structural  steel,  built-up  unit.  The  top  of 
the  flasks  forming  the  top  carriage  carry  the  trunnion  bearings  for 
the  cradle.  At  the  front  of  the  carriage  a  pintle  bearing  is  pro- 
vided, which  bears  on  the  pintle  of  the  platform,  thus  providing  a 
means  of  rotating  the  top  carriage  and  traversing  the  piece.  A 
pinion  at  the  rear  of  the  carriage  meshing  with  a  rack  on  the  plat- 


334 

form  swings  the  rear  end  of  the  carriage  in  traverse.  A  traverse  of 
10°  each  side  of  center  is  thus  obtained. 

A  windlass  mounted  on  the  top  carriage  is  used  for  setting  up  and 
dismounting  the  unit. 

At  the  rear  of  the  top  carriage  is  attached  a  loading  platform  on 
which  is  mounted  a  loading  crane  for  handling  the  shells.  On  the 
loading  platform  tracks  are  provided  for  a  rammer  car  which  is  used 
to  transport  a  projectile  from  the  loading  crane  to  the  breech  and  to 
ram  it  into  the  bore  of  the  howitzer.  This  ramming  of  the  projectile 
is  accomplished  by  means  of  a  movable  chain  on  the  rammer  car 
which  has  suitable  lugs  for  engaging  the  shell  and  is  operated  by 
cranks  on  the  rammer  car. 

The  platform  on  which  the  top  carriage  rests  is  a  structural-steel 
unit  composed  of  a  top  and  bottom  plate  secured  by  channels.  The 
middle  portion  is  open  and  has  a  trunk  section  to  provide  a  space 
for  the  howitzer  to  recoil  at  high  angles  of  elevation.  The  traversing 


METHOD   OF   LOWERING  PLATFORM. 

rack  is  secured  to  the  rear  end  of  the  platform.  Built-up  steel  floats 
are  attached  to  the  rear  of  the  platform  by  swinging  arms,  which 
function  to  give  stability  to  the  mount  at  extreme  angles  of  azimuth. 
Axle  brackets  and  attachments  for  the  false  trail  of  the  transport 
wagon  are  provided  for  use  when  traveling. 

Accessories. — A  considerable  number  of  tools  and  accessories  are 
required  for  the  erection,  operation,  and  maintenance  of  the  piece. 
The  principal  ones  are  as  follows :  Erecting  frame,  shot  truck,  sights, 
transport  wheel  tracks,  track  for  shot  truck,  shell  tongs,  shot  barrow, 
air  pump,  liquid  pump,  hydraulic  jacks,  wheel  blocks  and  mats,  axle- 
lifting  levers,  etc. 

The  erecting  frame  is  composed  of  structural-steel  beams.  It  is 
operated  by  hydraulic  jacks  and  is  used  in  assembling  and  dismount- 
ing the  piece.  It  may  also  be  used  as  a  derrick  for  handling  shells. 
When  used  for  this  purpose,  a  trolley  attachment  with  shell  tongs  is 
provided. 


335 


55160—21 22 


336 


337 

The  shot  truck  is  a  four-wheeled  vehicle  with  flanged  wheels  fitting 
a  track  which  is  laid  from  the  magazine  to  the  piece,  and  will  carry 
two  of  the  projectiles.  The  track  for  this  truck  is  600  millimeters 
(23f  inches)  gauge.  It  is  supplied  in  built-up  lengths  of  light  steel 
rails  joined  by  pressed-steel  ties. 

Weights,  dimensions,  and  ballistics. 

Weight   of  howitzer pounds—  10,  790 

Length   of  howitzer inches—  199.  6 

Rifling Right  hand,  1  turn  in  40  calibers  at  origin  to  1  turn  in  20 

calibers  at  a  point  24.369  inches  from  the  muzzle. 

Weight  of  powder  charge . pounds 38$ 

Weight  of  projectile do 356 

Muzzle  velocity ft.  per  sec 1,  700 

Maximum   range yards 18, 000 

Weight  of  howitzer  and  breech  mechanism pounds 10,  831 

Amount  of  traverse  (right  and  left) degrees 10 

Maximum  angle  of  elevation  of  howitzer do 60 

Maximum  angle  of  depression  of  howitzer do 1 

Loading   angle do 9i 

Normal  length  of  recoil inches 44.  83 

Maximum   recoil  allowable do 46.  73 

Height  to  center  of  trunnions do 64.  5 

Weight  of  howitzer  arid  transport  wagon pounds 15,  220 

Weight  of  cradle  and  transport  wagon do 14,  605 

Weight  of  top  carriage  and  transport  wagon do 12,  545 

Weight  of  platform  and  transport  wagon do 16,  230 

Weight  of  complete  unit  in  firing  position do 41,  296 

Weight  of  erecting  frame '. do 33,  024 

Sleigh    (complete,   filled   with   liquid  and   all   pistons,   packings,   caps, 

etc.) pounds 5,  747 

Cradle   (complete,  but  without  elevating  arms) - do 4,068 

Recuperator  (steel  forging  only),  completely  machined do 3,931 

Elevating  arms    (including  quick-loading  gear) do 855 

Top  carriage   (complete,  with  elevating  and  traversing  gear,  windlass, 

footboards,  bearing  caps,  traversing  rollers,  rear  clips,   draft  hook, 

cradle  lock,  jack  rollers,  etc.) pounds—  6,685 

Rammer    car • do 540 

Loading    platform do 555 

Loading-crane  bracket  and  loading  crane do 441 

Shell    tongs do 39 

Shot   truck do 430 

Platform      (complete,     with     pintle     springs,     swinging     arms,     and 

floats) pounds—  11,  895 

Transport  wheel  tracks  with  inclined  planes do 1, 175 

Erecting  frame  (complete,  with  hydraulic  jacks) do 3,024 


338 


240-MILLIMETER  HOWITZER  TRANSPORT  LIMBERS  AND 

WAGONS. 


In  order  to  transport  the  complete  carriage  there  are  provided 
four  transport  vehicles,  namely,  the  howitzer  transport  wagon,  top 
carriage  transport  wagon,  platform  transport  wagon,  and  cradle 
transport  wagon.  Each  wagon  consists  principally  of  a  limber,  false 
trail,  rear  axle,  and  wheels. 


HOWITZER   TRANSPORT   WAGON. 


The  limber  consists  of  two  wheels,  an  axle,  pole,  and  turning  arc, 
all  of  which  are  similar  for  each  wagon. 

The  pole  is  composed  of  two  steel  parts  joined  with  a  flexible 
spring  coupling,  consisting  of  a  coil  spring,  plunger,  and  hinged 
joint,  providing  a  movement  of  about  15  inches  at  the  end  of  the 


CRADLE   TRANSPORT   WAGON. 

pole  to  make  up  for  any  difference  in  height  between  the  limber 
and  the  vehicle  to  which  it  may  be  coupled.  This  spring  coupling 
also  relieves  the  vehicles  of  any  sudden  shocks  during  transportation. 
Each  limber  is  provided  with  a  pintle  over  which  fits  the  lunette 
ring  of  its  false  trail.  Safety  chains  are  attached  to  the  pole  to  hold 
the  false  trail  on  the  pintle  in  proper  position. 

(339) 


340 


The  turning  arc  is  attached  to  the  axle  and  the  false  trail  bears  on 
it  as  it  rotates  around  the  pintle. 

Four  false  trails  are  provided,  one  for  each  wagon.  They  are 
similar  in  most  respects,  especially  the  front  end  that  has  the  lunette 
ring.  This  lunette  ring  floats  in  the  trail  and  is  surrounded  by  coiled 
springs  which  take  up  the  shocks  incidental  to  transportation.  The 


TOP   CARRIAGE   TRANSPORT   WAGON. 

body  of  the  false  trail  is  formed  to  suit  the  heights  of  the  unit  to 
which  it  attaches  and  has  brace  rods  for  stiffening.  A  locking  ar- 
rangement is  provided  to  lock  the  units  to  the  false  trails  and  is 
operated  by  means  of  a  hand  lever. 

The  rear  axle  of  the  transport  wagon  is  made  of  a  special  forging 
shaped  to  suit  the  unit  which  it  carries.    The  axle  for  the  howitzer 


PLATFORM  TRANSPORT   WAGON. 

transport  wagon  is  curved  to  suit  the  radius  of  the  howitzer  and  has 
pawls  which  lock  the  howitzer  in  place. 

Band  brakes  are  used  and  are  alike  for  all  four  types  of  rear  axles, 
but  the  brake-operating  mechanism  is  different  for  the  various  trans- 
port wagons.  The  brakes  on  each  vehicle  are  connected  by  a  con- 
necting lever  shaft  which  is  operated  by  a  lever  with  ratchet  and 
pawl.  Provision  is  made  for  the  setting  of  the  brakes  by  the  operator 
of  the  hauling  tractor  by  means  of  a  rope  attached  to  the  operating 
lever  and  extending  to  the  tractor. 


342 

When  the  complete  carriage  is  set  up  for  firing,  the  transport 
vehicles  are  close  coupled  by  the  false  trail  and  form  short  units, 
having  four  wheels  which  can  be  drawn  away.  Brackets  are  provided 
attached  to  each  axle  for  the  brace  rods  which  are  used  when  the 
vehicles  are  unloaded  and  close  coupled. 

Both  the  limber  and  rear  axles  are  equipped  with  standard  rubber- 
tired  wheels. 

Weights  and  dimensions. 

Howitzer  and  transport  wagon  (complete) pounds 15,200 

Weight  of  transport  wagon  (close  coupled) do 4,385 

Weight  of  front  wheels  and  axle do 1, 185 

Weight  of  rear  wheels,  axle,  and  brake do 2.  750 

Weight  under  front  wheels do 4,  864 

Weight  under  rear  wheels do 10, 356 

Wheel  base inches—  162 

Overall  length do 314 

Cradle  (with  elevating  arms  and  sleigh)  transport  wagon pounds 14,605 

Weight  of  transport  wagon  (close  coupled) do 4,335 

Weight  of  front  wheels  and  axle do 1, 185 

Weight  of  rear  wheels,  axle,  and  brake do__  2,  700 

Weight  under  front  wheels do 3,  530 

Weight  under  rear  wheels do 11, 075 

Wheel  base inches 150 

Overall  length do 267 

Top  carriage  (with  rammer  car,  loading  platform,  loading  crane)  and 

transport  wagon pounds —  12,  545 

Weight  of  transport  wagon  (close  coupled) do 4,  285 

Weight  of  false  trail  complete  for  platform do 475 

Weight    of    false    trail    for    cradle,    howitzer,    and    top    carriage, 

each pounds 450 

Weight  of  front  wheels  and  axle do 1, 185 

Weight  of  rear  wheels,  axle,  and  brake do 2,  650 

Weight  under  front  wheels do 4,030 

Weight  under  rear  wheels do 8,  515 

Wheel  base inches—  181 

Overall  length do__  280 

Platform    and    transport    wagon     (including    brake    lever    and    draft 

hook) pounds—  16,  230 

Weight  of  transport  wagon  (close  coupled) do 4,335 

Weight  of  front  wheels  and  axle do 1, 185 

Weight  of  rear  wheels,  axle,  and  brake do 2,675 

Weight  under  front  wheels do 4,  485 

Weight  under  rear  wheels do 11,  745 

Wheel  base inches—  153 

Overall  length do 292 

Weight  of  limber  wheel pounds—  350 

Weight  of  transport  wagon  wheel __ do__  1.  050 

Howitzer  transport  wagon  (close  coupled) do__  4,385 

Cradle  transport  wagon  (close  coupled) do__  4,335 

Top  carriage  transport  wagon  (close  coupled) do—  4,285 

Platform  transport  wagon  (close  coupled) do 4,335 


343 

Maximum  width  of  transport  wagons  (platform) inches..  102 

Maximum  height  of  transport  wagons  (top  carriage) do 102 

Minimum  road  clearance  (distance  between  lowest  point  of  wagon  and 

ground ) inches 15 

Diameter  of  smallest  circle  in  which  a  transport  wagon  will  turn.do 544 

Wheels  on  transport  wagon,  rubber  tired do 60  by  8 

Wheels  on  limber,  rubber  tired do 49  by  4 

Limber  wheels : 

Width  of  track,  center  to  center  of  tire do 60. 83 

Bearing  surface do 3. 54 

Rear  wheels : 

Width  of  track,  center  to  center  of  tire do 63.  84 

Bearing  surface do 4.  74 

Maximum  width  of  widest  transport  wagon  (platform) do 102 

Maximum  height  of  highest  transport  wagon  (top  carriage) do 102 

Maximum  overall  length  of  longest  transport  wagon  (howitzer) do 314 


ANTIAIRCRAFT  ARTILLERY. 


In  considering  the  question  of  antiaircraft  materiel  it  is  to  be  re- 
membered that  the  science  of  antiaircraft  gunnery  has  changed  prob- 
ably to  a  greater  extent  than  that  of  any  other  branch  of  the  service. 
It  was  unheard  of  at  the  beginning  of  the  war,  and  in  consequence 
has  grown  from  nothing  at  all  to  an  important  phase  of  operations. 
As  a  result,  materiel  is  constantly  changing  and  can  not  be  said  to 
have  reached  a  definite  basis  even  at  this  time.  The  materiel  was 
greatly  affected  also  by  the  change  from  "  position  warfare  "  to  war- 
fare of  motion;  portability  changing  from  a  somewhat  neglected 
factor  to  one  of  paramount  importance. 

In  field  artillery  practice,  range  problems  are  presented  in  connec- 
tion with  mortars,  howitzers,  and  guns,  but  the  results  to  be  accom- 
plished and  the  problems  in  connection  with  each  of  these  weapons 
are  quite  different.  The  provided  elevation  of  the  guns  of  some  cali- 
bers is  small,  while  the  muzzle  velocity  of  some  of  the  howitzers  and 
all  of  the  mortars  is  comparatively  low ;  also  the  traverse  of  all  three 
different  types  of  weapons  is  limited.  The  field  target  is  usually  sta- 
tionary, maps  being  available  for  establishing  its  position,  and  ample 
time  is  available  in  which  to  figure  its  range.  Observation  of  the 
point  of  fall  of  one  shot  serves  as  a  guide  in  correcting  the  range  for 
the  next  shot.  Frequently  it  is  possible  to  choose  atmospheric  condi- 
tions under  which  the  weapon  would  be  employed,  and  assisting  or 
opposing  longitudinal  windage,  or  driftage  due  to  side  windage,  is 
calculated  with  the  aid  of  wind  gauges. 

For  antiaircraft  service  the  problem  is  entirely  different.  The 
single  weapon  must  be  able  to  cover  the  elevations  of  all  three  types 
of  the  field  artillery  weapons  and  preferably  have  a  traverse  of  360°. 
These  wide  variations  in  elevation  introduce  serious  recoil  problems, 
and  the  difference  in  the  traverse  problem  may  be  to  some  extent 
illustrated  by  reference  to  the  fact  that  the  total  traverse  of  the  75- 
millimeter  French,  model  1897  MI,  field  gun  is  only  6°. 

Instead  of  a  stationary  target  there  may  be  presented  one  whose 
speed  is  one-sixth  of  the  speed  of  the  projectile  itself  and  whose 
course  can  in  no  wise  be  forecast  by  road  direction  or  terrain  forma- 
tion and  whose  position  may  be  at  any  vertical  or  horizontal  angle. 
The  possible  altitude  and  speed  of  airplanes  increased  from  time  to 
time,  making  useless  the  earlier  and  present  basic  data  to  be  employed 
in  the  design  of  protective  materiel.  Under  certain  conditions  of  air- 
plane approach  the  range  must  be  calculated  on  the  instant  and  there 
is  no  choice  as  to  atmospheric  conditions.  As  the  target  is  not  sta- 
tionary, range  corrections  are  difficult  to  estimate  by  observation. 

(344) 


345 


While  gauges  may  indicate  the  direction  and  force  of  the  wind  at 
the  altitude  at  which  they  are  set.  they  furnish  no  indication  of  air 
currents  existing  at  other  altitudes  through  which  it  might  be  neces- 
sary for  the  antiaircraft  projectile  to  pass.  With  the  flat  trajectory 
of  a  fieldpiece  at  but  a  few  degrees  elevation,  the  density  of  atmos- 
phere through  which  the  projectile  must  pass  is  largely  uniform, 


while  at  high  angles  of  fire  with  antiaircraft  guns  the  projectile 
passes  through  atmospheres  of  different  rarefactions,  and  hence  dif- 
ferent resistances  to  the  passage  of  the  projectile.  These  influences 
affect  the  trajectory  of  the  projectile,  the  rate  of  travel  of  the  projec- 
tile, and  the  time  element  of  the  burning  of  the  fuze. 

With  field  artillery,  shrapnel  is  employed  with  both  a  time  fuze 
and  an  impact  fuze,  and  high-explosive  shell  with  impact  fuze  only, 


346 

but  antiaircraft  projectiles  are  fitted  only  with  time  fuzes,  as  other- 
wise a  projectile  which  has  missed  its  aerial  mark  would  be  apt  to 
cause  damage  within  friendly  lines  through  impact  explosion  on 
reaching  the  ground. 

As  there  is  practically  no  position  which  is  entirely  free  from  the 
possibility  of  aircraft  attack,  and  as  there  is  no  means  of  determin- 
ing the  direction  from  which  such  attack  may  come,  ready  mobility 
of  antiaircraft  guns  is  most  desirable,  and  as  opportunity  to  reach 
the  target  is  frequently  only  momentary,  rapidity  of  sighting  and  of 
firing  is  essential.  In  the  case  of  indirect  fire  from  a  camouflaged 
position,  the  gunner  has  not  even  had  a  view  of  the  approaching 
plane,  but  must  lay  his  gun  on  the  basis  of  telephone  data,  or  data 
otherwise  transmitted  from  the  battery  commander's  station. 

The  antiaircraft  target  may  be  a  balloon — either  stationary  or 
towed — a  dirigible,  or  an  airplane,  but  is  most  frequently  the  latter. 
Location  of  the  position  of  balloons  or  dirigibles  is  comparatively 
simple,  as  compared  with  airplane  location,  owing  to  the  size  of  the 
target  and  the  stationary  position  or  low  speed  of  motion.  For  night 
fire,  searchlights  or  other  illuminating  means  are  required,  and  for 
night  fire  or  protective  fire  in  thick  weather,  sound-locating  devices 
are  employed. 

The  earlier  fire  from  antiaircraft  artillery  was  directed  solely  from 
the  burst;  that  is,  by  firing  a  shot,  and  judging  the  direction  of 
the  next  shot  solely  by  observation  of  the  nearness  to  which  the  burst 
of  the  first  shot  had  approximated  the  position  of  the  target.  In  the 
meantime,  however,  the  position  of  the  target  had  changed.  This 
system  has  given  way  to  the  use  of  an  elaborate  system  of  instruments 
for  the  determination  of  fire  in  accordance  with  certain  established 
principles. 

In  the  attack  upon  aircraft  the  desired  end  may  be  accomplished 
either  by  the  destruction  of  the  aircraft  itself  or  by  the  disabling 
of  its  occupants,  in  which  latter  case  the  destruction  of  the  aircraft 
would  follow.  The  methods  adopted  include  destruction  by  incen- 
diarism, by  direct  hits,  by  flying  particles  from  exploding  shell  or 
shrapnel,  and  by  shell  shock.  Methods  of  fire  may  involve  explosive 
projectiles  from  a  single  gun,  salvos  or  barrage  fire  from  a  number 
of  guns,  rapid  firing  from  pom-poms  (small  caliber  guns,  firing  ex- 
plosive projectiles),  or  from  machine  guns  firing  small-arms  ammu- 
nition. 

Because  of  the  important  field  played  by  aerial  sound-detecting 
apparatus,  searchlights,  and  telephony,  including  wireless,  future 
progress  in  the  design  of  antiaircraft  artillery  will  consider  these 
subjects.  With  the  perfection  of  airplane  motors  and  their  inter- 
connected functioning  apparatus,  the  design  of  aircraft,  and  the  art 
of  flying,  other  factors  upon  which  the  design  of  artillery  equipment 
should  likewise  be  based,  enter  into  this  problem. 


347 


3-INCH  ANTIAIRCRAFT  GUN  MATERIEL,  MODEL  1918. 


It  is  hardly  possible  to  estimate  how  great  will  be  the  future  im- 
portance of  the  perfection  of  the  country's  aerial  defense  from  a 
strategic  point  of  view.  Aviation  as  an  offensive  arm  will  remain  a 
principal  arm,  and  antiaircraft  artillery,  as  a  defensive  branch,  will 
play  the  part  that  coast  artillery  plays  to  the  naval  squadrons. 

Antiaircraft  gunnery  differs  from  other  forms  of  gunnery,  such 
as  field-artillery  problems.  It  is  a  new  subject,  one  more  compli- 
cated than  any  other  artillery  problem,  and  consequently  one  which 
essentially  demands  new  methods  and  modes  of  measurement. 

Development  has  gradually  led  to  the  design  of  the  3-inch  auto- 
trailer  carriage,  which  consists  of  a  3-inch  gun,  model  1918,  anti- 
aircraft, and  a  3-inch  autotrailer  carriage,  model  of  1917.  mounted 
on  a  four-wheel  trailer  truck,  having  springs  and  solid  rubber  tired 
wheels.  The  gun  and  the  mount  remain  fixed  on  the  trailer,  both  in 
traveling  and  in  battery  positions. 

The  muzzle  velocity  of  the  gun  is  2,400  foot-seconds.  Both 
shrapnel  and  high-explosive  shells,  each  weighing  about  15  pounds, 
are  employed.  At  a  maximum  elevation  of  85°  the  maximum  ver- 
tical ordinate,  limited  by  the  time  fuze,  is  7.940  meters.  At  minimum 
elevation  of  10°  the  projectile  strikes  the  ground  at  approximately 
6,100  meters.  At  23°  elevation  the  bursting  vertical  ordinate  is 
1,176  meters  and  the  horizontal  ordinate  approximately  7,025  meters. 

The  recoil  mechanism  is  similar  to  that  employed  with  the 
American  75  millimeter,  model  1916,  field  gun,  but  with  the  use  of  a 
spearhead  counter-recoil  buffer.  This  recoil  mechanism  is  of  the 
hydro-spring  type  and  the  variable  adjustment  of  the  stroke  is  gov- 
erned by  a  rotating  valve,  the  movement  of  which  moves  port  holes 
behind  the  edges  of  three  lands  permitting  the  passage  of  oil  to  the 
by-passing  recesses. 

The  anti-aircraft  gun,  together  with  the  recoil  mechanism,  is  held 
by  the  cradle  and  swings  from  10°  to  85°  elevation  in  the  trunnion 
bearings  of  the  top  carriages.  A  base  plate  rigidly  bolted  to  the 
trailer  chassis  supports  the  top  carriage  on  traversing  rollers  on 
which  the  top  carriage  rotates  360°  in  azimuth  around  a  pintle  on  the 
base  plate. 

(348) 


349 


350 

The  trailer  carriage  is  equipped  with  outriggers.  Stability  and 
lifting  jacks  which,  when  in  firing  position,  rest  on  detachable 
floats  on  the  ground,  support  the  entire  weight  of  carriage  and 
trailer.  These  outriggers  and  jacks  are  employed  to  stabilize  this 
unit  when  in  action  and  to  prevent  the  mount  from  overturning 
when  the  gun  is  fired  at  low  angles  of  elevation. 


VIEW  OF  REAR  OUTRIGGERS  FOLDED;  OUTSIDE  END  OF  RIGHT  OUTRIGGER  BRACE 
READY  TO  BE  PLACED  IN  RECEPTACLE;  SCREW  JACK  WITH  OUTRIGGERS 
FOLDED. 

In  traveling  position  the  outriggers  are  folded  up,  the  jack  screws 
raised,  and  the  floats  and  spades  carried  in  another  vehicle,  with 
the  exception  of  the  stability  jack  floats,  which  are  attached  to  the 


55160—21 


(352) 


353 

jack  screws.  Traveling  locks  are  provided  to  lock  the  gun  at  about 
20°  elevation  to  protect  the  elevating  mechanism.  In  azimuth  the 
carriage  is  locked  lengthwise  of  the  trailer  to  remove  unnecessary 
strains  from  the  traversing  mechanism  when  the  unit  is  traveling. 

Adjustable  seats  and  foot  rests  for  the  gunners  and  platforms  that 
fold  up  when  traveling  are  fastened  to  the  top  carriage.  This  unit 
is  considered  able  to  traverse  over  any  roads  suitable  for  field  ar- 
tillery. Weight  of  complete  unit  is  approximately  14,000  pounds. 

Fixed  ammunition  is  used  with  these  guns,  consisting  of  time- 
fuzed  high-explosive,  illuminating  shell,  tracer  shell,  and  shrapnel. 
All  the  shell  and  shrapnel  are  issued  fuzed. 

3-INCH  AUTOTRAILER  CARRIAGE. 

The  3-inch  autotrailer  carriage  consists  of  a  3-inch  gun,  model  of 
1918,  antiaircraft,  and  a  3-inch  autotrailer  carriage,  model  of  1917, 
mounted  on  an  autotrailer. 

The  gun,  of  which  there  are  two  models,  1918  and  1918  MI,  is  built 
up  of  nickel-steel  forgings  and  consists  of  a  tube,  a  jacket,  and  a 
breech  ring,  the  latter  being  screwed  to  the  rear  end  of  the  jacket 
forming  a  housing  for  the  breech  mechanism.  Lugs  are  provided  at 
the  top  and  bottom  of  the  breech  ring,  to  which  are  secured,  respec- 
tively, the  recoil  cylinder  and  counter- recoil  spring  rods.  The  1918  MI 
model  differs  from  the  1918  model  only  in  the  jacket,  which  is  1.6 
inches  longer  at  the  threaded  part,  allowing  a  greater  thickness  of 
metal  in  rear  of  the  jacket,  thereby  strengthening  the  gun  around 
the  chamber. 

The  breech  mechanism  is  practically  the  same  as  that  used  on  the 
75-millimeter  field  gun,  model  of  1916  (American)  (see  p.  75),  being 
of  the  drop  block  type,  semiautomatic,  and  operated  by  a  handle  on 
the  right  side  of  the  breech,  which  is  pulled  backwards  and  down  to 
open  the  breech. 

Weights,  dimensions,  and  ballistics  of  gun. 

Weight  of  gun  (including  breech  mechanism) pounds 1,966 

Caliber inches—  3 

Total  length  of  gun do 129.69 

Length  of  bore do 120 

Volume  of  chamber cu.  in__  200 

Length  of  rifled  portion  of  bore inches..  95.  87 

Number  of  grooves 24 

Width  of  grooves inches..  0.2927 

Depth  of  grooves do 0.  03 

Width  of  lands dc 0. 10 

Muzzle  velocity ft.  per  sec__  2,400 

Maximum  range yards 12. 140 

Twist,  right  hand  increasing  from  one  turn  to  50  calibers  at  the  origin 

to  one  turn  in  25  calibers  at  a  point  8.87  inches  from  the  muzzle  and 

uniform  from  that  point  to  the  muzzle. 


354 

The  carriage  comprises  the  top  carriage  and  cradle.  The  top 
carriage  consists  of  two  side  frames  bolted  to  a  bottom  plate  which 
in  turn  rests  on  a  circular  roller  frame  and  rotates  about  a  pintle  on 


VIEW  OF  RIGHT  REAR  OUTRIGGER  WITH  JACKSPADE  AND  FLOAT  REMOVED  AND 
BRACE  DROPPED  FROM  SHACKLE  AT  INSIDE  END;  LEFT  REAR  OUTRIGGER  IN 
POSITION.  WITH  FLOAT  CONNECTION  FOLDED. 

the  base  plate.  The  base  plate  is  rigidly  bolted  to  the  trailer  chassis 
and  is  equipped  with  outriggers  and  stability  and  lifting  jacks  which, 
when  in  firing  position,  rest  on  detachable  floats  on  the  ground  and 
support  the  entire  weight  of  the  carriage  trailer.  The  top  carriage 


355 


is  prevented  from  tipping  or  lifting  from  the  tranversing  rollers  by  a 
front  and  rear  clip  which  are  fastened  to  the  bottom  plate  and  which 
engage  an  annular  flange  on  the  base  plate. 


The  recoil  mechanism  is  of  the  variable  recoil  hydro-spring  type 
and  operates  the  same  as  that  of  the  75-millimeter  field  gun,  model 
of  1916.  The  only  noticeable  difference  between  the  two  is  that  a 


356 

spear  buffer  is  used  instead  of  a  valve  in  the  buffer  rod  head  as  is 
used  in  the  75-millimeter  gun.  The  length  of  recoil  varies  from  16 
inches  at  85°  elevation  to  40  inches  at  10°  elevation. 

An  elevating  arc  having  teeth  is  secured  to  the  lower  side  of  the 
cradle  and  meshes  with  a  Hindley  worm  which  is  driven  through 
bevel  and  spur  gears  by  a  handwheel  located  on  the  right  side  of  the 
top  carriage. 

The  traversing  mechanism  is  attached  to  the  left  side  of  the  top 
carriage.  The  handwheel,  through  bevel  gears,  a  worm,  a  worm 
wheel,  and  a  friction  clutch,  rotates  a  pinion  which  in  turn  meshes 
with  an  annular  rack  bolted  to  the  base  plate.  The  pinion  when 
rotated  causes  the  top  carriage  to  revolve  about  its  pintle  on  the 
traversing  rollers. 

Four  seats  are  attached  to  the  top  carriage,  two  on  either  side, 
which  are  used  by  the  personnel  who  operate  the  sights  and  elevating 
and  traversing  mechanisms. 

Platforms  are  bolted  to  both  sides  at  the  rear  of  the  top  carriage 
for  the  personnel  who  load  and  fire  the  piece.  The  platforms  may 
be  folded  up  and  the  seats  swung  to  one  side  for  traveling. 

When  traveling,  the  gun  is  locked,  at  an  elevation  of  about  20° 
and  lengthwise  of  the  trailer,  by  upper  and  lower  traveling  locks  for 
the  purpose  of  taking  up  any  strains  or  shocks  which  might  come  on 
the  elevating  or  traversing  mechanisms. 

Weights  and  dimensions  of  carriage. 

Weight  of  carriage  unit  complete   (including  spare  ammunition  chest 

filled  with  ammunition,  tools,  and  accessories) pounds 14,085 

Weight  of  cradle  (recoil  cylinder  complete,  including  oil,  trunnions,  gun 
slides,  piston  rod  bracket  complete,  and  spring  cylinder  with  springs 

assembled) pounds 1, 203 

Weight  of  trailer   (with  ammunition  chest  only,  without  tools  and  ac- 
cessories or  ammunition) pounds 4,085 

Weight  of  trailer  with  carriage,  gun,  and  ammunition  chest  only do 13,  200 

Weight  under  front  wheels  (fully  equipped) do 7,075 

Weight  under  rear  wheels  (fully  equipped) do 7,010 

Weight  of  one  round  of  ammunition  (complete) do 26.  8 

Maximum  angle  of  elevation degrees--  85 

Minimum  angle  of  elevation do 10 

Traverse  of  carriage do 360 

Maximum  length  of  recoil inches 40 

Minimum  length  of  recoil do 10 

Number  of  rounds  in  ammunition  chest 14 

Number  of  rounds  in  spare  ammunition  chest 16 

Height  from  ground  to  center  of  trunnions inches__ 

Height  from  ground  to  top  of  gun  (in  traveling  position) do 119 

Maximum  width  of  carriage do 77 

Maximum  length  of  carriage  (drawbar  up) do 230 

Maximum  length  of  carriage  (drawbar  down) do 243 


357 


358 


The  trailer  upon  which  the  carriage  is  mounted  consists  of  two 
parallel  side  frames,  between  which  are  secured  the  cross  members, 
and  bracing  making  up  the  complete  chassis.  Between  the  front  and 
rear  wheels  the  frame  is  so  depressed  that  the  base  plate  of  the  car- 
riage is  on  the  same  plane  as  the  hubs  of  the  wheels,  thus  bringing 
the  center  of  gravity  of  the  carriage  lower  and  lessening  the  possi- 
bility of  overturning.  The  space  at  the  front  of  the  trailer  formed 
by  the  side  frames  and  cross  members  is  provided  with  a  bottom 


FRONT  VIEW  OF  TRAILER. 

plate,  a  top  plate,  and  hinged  cover,  and  is  utilized  as  a  tool  box. 
The  rear  section  is  similar  to  the  front,  except  that  a  support  is 
provided  for  the  ammunition  chest.  The  chest  which  carries  16 
rounds  of  ammunition  also  serves  as  a  seat  for  the  operators  of  the 
carriage.  A  foot  rest  is  fastened  to  the  rear  tool  box  cover.  The 
chassis  is  supported  on  the  axles,  both  front  and  rear  by  semiellipti- 
cal  springs. 

The  trailer  is  towed  and  steered  by  a  drawbar  equipped  with  a 
lunette  and  fastened  to  the  front  axle  in  such  a  manner  that  the 


(360) 


361 

trailer  will  actually  follow  in  the  path  of  the  truck  or  tractor  by 
which  it  is  drawn.  The  trailer  may  also  be  steered  by  the  rear 
wheels  when  the  rear  wheel  lock  is  released  and  the  steering  bar  is 
inserted.  A  pintle  is  provided  on  the  rear  end  of  the  trailer  to  ac- 
commodate any  vehicles  which  may  be  attached  thereto. 

This  vehicle  is  equipped  with  a  brake  of  the  internal  expanding 
type  operating  within  drums  attached  to  the  rear  wheels  and  applied 
and  released  by  a  lever  on  the  right  side  of  the  trailer  by  one  of  the 
personnel  seated  on  the  ammunition  chest. 

W-eights  and  dimensions  of  trailer. 

Wheelbase inches 156 

Width  of  track do 60 

Length  of  frame  over  all do 200 

Width  of  frame  over  all do 48. 125 

Weight  of  chassis pounds 3, 800 

Size  of  tires inches 37 

Width  of  tires do 6 

Height  from  ground  to  center  line  of  drawbar do 15 

Height  from  ground  to  top  of  frame,  empty do 13 

Diameter  of  brake  drum do 16. 625 

Turning  radius , feet 28.  6 

Road  clearance  under  front  axle inches 10.  281 

Road  clearance  under  rear  axle do 11.  375 

Height  from  ground  to  center  line  of  pintle do 20.  5 

Over-all  width  at  widest  part do 77. 25 

Center  to  center  of  spring  pads  (front) do 28.5 

Center  to  center  of  spring  pads  (rear) do 28.  5 

The  sight  issued  for  antiaircraft  carriages,  model  of  1918,  consists 
of  two  units,  one  being  mounted  on  the  right  trunnion  of  the  cradle 
and  the  other  on  a  bracket  attached  to  the  left  side  of  the  carriage, 
the  two  units  being  connected  by  a  coupling  shaft.  The  elements  on 
the  right  side  are  the  range  and  elevation  corrector  and  those  on  the 
left  side  are  the  angle  of  site  and  deflection  corrector.  An  open  sight 
is  attached  to  the  sight  proper  for  rapid  location  of  the  target. 

All  necessary  points  for  night  firing  are  illuminated  by  the  elec- 
trical equipment.  A  6- volt  system  is  used,  the  current  being  supplied 
by  dry  batteries,  storage  battery,  or  by  a  manually  operated  genera- 
tor. Small  lamps  of  one  or  two  candlepower,  shielded  by  reflectors, 
are  used  to  illuminate  the  necessary  scales  and  cross  hairs. 


362 


3-INCH  ANTIAIRCRAFT  GUN  MOUNT,  MODEL  OF  1917. 


The  principal  use  of  antiaircraft  artillery  is  to  hinder  avia- 
tors from  carrying  out  their  missions.  The  destruction  of  airplanes, 
with  the  means  actually  at  its  disposal,  is  still  a  question  of  luck. 
Experience  has  taught  aviators  to  defend  themselves  against  fire  by 
continual  changes  in  direction. 

The  earlier  antiaircraft  artillery  fire  was  directed  by  observation 
of  the  burst,  but  that  eventually  gave  away  to  direction  of  the  fire 
by  carefully  deduced  principles.  Nevertheless,  the  antiaircraft  ar- 
tillery theory  lays  but  little  stress  upon  the  possibility  of  inflicting 


GUN    MOUNT    IN    ACTION. 

damage  through  a  direct  hit  by  the  projectile  which  is  fired  from  the 
gun,  as  it  is  considered  that  the  possibility  of  such  hit  is  too  remote. 
The  artillery  practice  is,  therefore,  to  so  direct  the  projectile  that  it 
will  explode  at  a  more  or  less  predetermined  position  and  cause 
damage  either  by  the  fragmentation  of  the  projectile,  which  covers 
a  very  much  larger  area  than  the  intact  projectile,  or  through  the 
concussion  caused  by  the  exploding  projectile,  the  effect  of  which 
would  also  be  felt  through  a  considerable  sphere. 

No  one  type  of  antiaircraft  gun  carriage  or  mount  can  possibly 
satisfy  all  conditions  of  modern  warfare.     It  is,  however,  possible 

(363) 


364 


365 


to  design  a  standard  gun  and  top  carriage  having  a  wide  range  of 
action  and  by  means  of  interchangeability  enable  this  mount  to  be 
used  on  either  a  truck  mount,  a  two  or  four  wheel  trailer,  a  cater- 
pillar tread  trailer,  or  as  a  semifixed  mount,  as  each  of  these  types 
of  vehicles  has  its  own  sphere  of  action.  However,  the  problem 
of  seacoast  defense  and  for  the  defense  of  depots,  etc.,  led  to  the 
design  of  the  3-inch  antiaircraft  gun  mount,  model  of  1917. 

The  3-inch  antiaircraft  mount  is  of  the  barbette  type,  with  con- 
stant recoil,  designed  to  be  mounted  on  a  solid  concrete  base  about 


VIEW   SHOWING   RIGHT   SIDE   OF  MOUNT. 

30  inches  thick  and  18  feet  in  diameter.  The  gun  mount  is  designed 
to  mount  the  3-inch  antiaircraft  gun,  model  1917,  1917  MI,  or  1917 
Mil,  commonly  known  as  the  15-pounder  gun. 

The  gun  has  a  12-inch  recoil  and  a  muzzle  velocity  of  2,600  foot- 
seconds.  Both  high  explosive  shell  and  shrapnel  may  be  employed, 
the  weight  of  the  projectile  being  15  pounds,  and  of  the  complete 
round  of  fixed  ammunition  28.38  pounds. 

The  gun  is  mounted  on  a  cradle  of  the  sleeve  type,  which  also 
serves  as  a  housing  for  the  spring  and  recoil  systems.  The  cradle  is 


366 

suspended  by  the  trunnions  from  the  top  of  the  pivot  yoke.  The 
pivot  yoke  is  bolted  to  the  racer,  which  rests  and  revolves  on  30 
rollers  on  the  roller  path  of  the  base  plate.  The  base  plate  is  held 
in  position  in  the  emplacement  by  16  anchor  bolts  set  in  the  concrete. 

The  field  of  fire  is  360°  traverse,  and  0°  to  90°  elevation.  Remov- 
able stops  are  provided,  however,  to  limit  the  elevation  to  85°,  due 
to  possible  injury  to  the  personnel  when  the  piece  is  fired  at  a  higher 
angle. 

Fixed  ammunition  is  used  in  these  guns,  consisting  of  a  tune- fuzed 
high-explosive  shell,  illuminating  shell,  tracer  shell,  and  shrapnel. 
Each  round  consists  of  the  cartridge  case  with  its  primer  and  powder 
charge ;  also  the  filled  and  fuzed  projectile. 

Weight,  dimensions,  and  ballistics. 

Weight pounds—     3, 105 

Caliber inches—  3 

Total  length do 174. 65 

Length  of  bore  in  calibers 55 

Length  of  rifled  portion  of  bore inches 137.  28 

Rifling : 

Number  of  grooves 24 

Width  of  grooves inch__  0.22927 

Depth do 0.03 

Twist,  right  hand,  1  turn  in  50  calibers  at  origin  to  turn  in  25  calibers 
at  9.28  inches  from  muzzle ;  thence  uniform. 

Weight  of  projectile,  filled  and  fuzed pounds—          15 

Weight  of  charge do 5.  32 

Weight  of  fixed  ammunition  (1  round) do 28.375 

Travel  of  projectile __inches__  139.33 

Volume  of  chamber cu.  in 296 

Muzzle  velocity ft.  per  sec__     2,600 

Maximum  pressure  per  square  inch pounds 32,000 

Maximum  horizontal  range yards —  12,  755 

Maximum  vertical  range do 9,  000 

The  model  of  1917  gun  is  built  up  of  alloy  steel,  consisting  of  tube, 
jacket,  and  locking  hoop.  The  jacket  envelops  the  rear  portion  of 
the  tube  and  forms  the  recess  or  seat  for  the  breech  mechanism.  A 
recoil  lug  projects  from  the  upper  surface  of  the  jacket  near  its 
extreme  end  and  affords  a  point  of  attachment  for  the  piston  rod  of 
the  recoil  cylinder.  A  lug  also  projects  from  the  under  surface,  to 
which  are  attached  the  counterrecoil  spring  rods.  The  locking  hoop 
is  forced  on  the  tube  and  forward  end  of  the  jacket,  securing  the 
latter  against  any  rearward  movement  of  the  tube  under  firing 
stresses. 

The  model  of  1917  MI  gun  is  similar  in  general  construction  to 
the  model  of  1917  gun,  except  that  instead  of  the  breech  ring  being 
integral  with  jacket,  it  is  a  separate  piece.  The  breech  end  of  jacket 
is  threaded  to  receive  the  breech  ring,  which  is  screwed  and  shrunk 
on  the  jacket  and  held  by  a  lock  screw.  The  locking  hoop  is  omitted 


367 


55160—21 24 


368 


nnm 

j  £  t  «  w  o 


369 

The  model  of  1917  Mil  is  similar  in  general  construction  to  the 
model  of  1917  MI,  except  in  the  method  of  securing  the  latch  plate 
to  the  gun.  On  the  models  of  1917  and  1917  MI  the  latch  plate 
is  secured  to  the  gun  by  screws,  while  on  the  1917  MI  the  latch  plate 
is  secured  to  gun  by  means  of  a  lug. 

The  breech  recess  is  rectangular  in  shape.  Two  extractor  trun- 
nion seats,  one  in  each  side,  are  cut  to  the  proper  radius  for  the 
extractor  to  rotate  and  slide.  Two  holes  are  drilled  from  the  rear 
face  of  the  breech,  one  on  each  side,  to  accommodate  a  spring  and 
plunger  which  press  against  the  hub  of  the  extractor,  keeping  it  in 
place  and  also  aids  the  extractor  in  ejecting  the  cartridge  case. 

The  breech  mechanism  consists  of  the  following  parts:  Breech- 
block, operating  lever,  operating  handle,  operating  cam,  operating 
cam  cover,  trigger  shaft,  extractors,  firing  mechanism,  latch,  and 
closing  spring  case. 

The  breechblock  is  of  the  drop-block  type  and  is  rectangular  in 
shape.  Two  grooves  run  lengthwise  on  the  block,  giving  a  wedging 
effect  against  the  end  of  the  cartridge  case  when  the  block  is  closed, 
and  when  opened,  insuring  a  clearance  between  the  cartridge  case 
and  the  block,  thus  eliminating  any  chance  of  the  cartridge  case  jam- 
ming. A  venthole  permits  the  escape  of  gas  from  a  ruptured  primer. 

Two  extractor  grooves,  one  on  each  side  of  the  block,  are  cut 
parallel  to  the  guide  grooves  and  curve  to  a  certain  cam  develop- 
ment which  permits  the  proper  action  of  the  extractors.  At  the  top 
of  the  block  a  radius  is  cut  to  permit  of  clearance  when  inserting 
the  projectile.  The  toe  of  each  extractor  is  cut  to  a  radius  which 
will  just  slide  along  the  body  of  the  cartridge  when  in  place  and 
engage  the  rim  of  the  cartridge  case. 

The  firing  mechanism  belongs  to  that  type  known  as  the  con- 
tinuous-pull mechanism;  that  is,  no  cocking  of  the  firing  pin  is 
required  other  than  a  pull  on  the  lanyard  or  trigger  shaft.  This 
arrangement  permits  of  repetition  of  the  blow  from  the  firing  pin 
in  case  of  a  misfire  as  often  as  desired  without  the  opening  of  the 
mechanism. 

Weights,  mount,  etc. 

Weight  of  mount  only pounds--  12, 175 

Weight  of  gun  and  mount do 15,  280 

Weight  of  gun  and  cradle do 7, 105 

Weight  of  cradle  and  recoil  systems do 4, 000 

Weight  of  yoke  with  elevating  and  traversing  mechanisms do 5, 100 

Weight  of  traversing  rack,  friction  band,  roller  cage,  and  base  plate_do 3, 000 

Weight  of  sight  and  supports do 75 

The  mount  is  emplaced  in  a  concrete  emplacement,  in  which  16 
anchor  bolts  are  set,  and  depressions  provided  for  8  leveling  screw 
thrust  plates.  A  niche  for  an  outlet  box,  through  which  electrical 
connections  are  made  to  the  main  base,  or  for  a  storage  battery  when 


370 

generated  current  is  not  available,  is  constructed  in  the  concrete 
to  meet  the  requirements  of  the  mount. 

This  emplacement  is  constructed  by  the  Engineer  Corps,  which 
also  furnishes  and  installs  the  necessary  outlet  or  storage  battery 
and  furnishes  the  plug  box,  portable  lamp,  cable,  and  plug. 

The  principal  parts  of  the  mount  are  the  base  plate ;  racer ;  pivot 
yoke;  cradle  (containing  recoil  cylinder  and  counterrecoil  mechan- 
ism) ;  traversing  mechanism,  including  traversing  rollers  and  dis- 
tance ring;  elevating  mechanism;  firing  mechanism;  illuminating 
circuit;  and  sight. 

The  base  plate  is  a  circular  steel  casting  which  rests  on  the  concrete 
emplacement  with  its  upper  surface  machined  to  form  the  lower 
roller  path.  Sixteen  holes,  equally  spaced  around  the  circumference 
of  the  flange,  are  provided  to  receive  the  foundation  bolts  which 
retain  the  base  plate  in  its  proper  position  in  the  emplacement.  A 
cylindrical  projection  in  the  center  forms  on  its  interior  the  housing 
for  the  360°  electrical  contact,  and  on  its  exterior  receives  the  trav- 
ersing rack. 

The  racer  is  a  circular  steel  plate,  upon  which  the  pivot  yoke  is 
bolted.  The  under  surface  is  machined  to  form  the  upper  roller 
path,  and  the  upper  surface  to  fit  the  yoke.  The  racer  rests  on  the 
rollers  and  rotates  freely  about  the  hub  on  the  traversing  rack.  Two 
clips,  front  and  rear,  are  bolted  to  the  under  side  of  the  racer,  and 
engage  with  a  lug  on  the  base  plate  to  prevent  the  racer  from  leaving 
the  rollers,  and  overturning  the  mount,  when  the  gun  is  fired. 

The  pivot  yoke  is  a  steel  casting,  consisting  of  two  vertical  side 
frames  joined  in  front  by  a  transom.  At  the  top  of  each  frame  is  a 
trunnion  bearing  and  trunnion  cap  lined  with  bronze  bushings. 
Tapped  holes  are  provided  in  the  left  frame  for  the  depression  and 
elevation  stop.  The  distance  ring  is  a  circular  bronze  ring  provided 
with  spaces  and  bearings  for  the  traversing  rollers.  The  traversing 
rollers,  30  in  number,  are  interposed  between  the  roller  paths  of  the 
base  plate  and  racer,  bearing  the  weight  of  the  mount.  The  rollers, 
roller  paths,  traversing  rack,  and  pinion  are  protected  from  the  en- 
trance of  dust,  sand,  or  grit  by  dust  guards.  The  oil  grooves  on  the 
circumference  of  the  distance  ring  serve  to  distribute  oil  from  the 
holes  in  the  flange,  forming  the  base  of  the  yoke,  to  the  axles  of  the 
rollers.  A  friction  band,  resting  on  the  base  plate,  is  made  to  grip 
the  traversing  rack.  To  adjust  this  band,  which  allows  slipping 
of  the  traversing  rack  to  protect  the  teeth  of  the  traversing  pinion 
from  too  heavy  a  stress,  a  cover  in  the  base  of  the  yoke  is  removed, 
giving  access  to  the  parts  beneath. 

Motion  of  the  mount  in  azimuth  is  obtained  by  a  traversing  pinion 
and  shaft,  the  pinion  meshing  with  the  teeth  of  the  traversing  rack. 
Power  is  transmitted  from  the  traversing  handwheel  to  the  traversing 


371 


372 


373 

worm,  thence  to  the  mount  through  a  set  of  gears  and  a  clutch 
mounted  in  the  traversing  gear  case.  Two  speeds  of  traverse  are 
possible  upon  throwing  the  clutch  in  by  means  of  a  handle,  so  that 
high  or  low  speed  gears  are  connected  to  the  upper  traversing  shaft. 

The  elevating  mechanism  consists  of  an  elevating  rack  keyed  to  the 
underside  of  the  cradle,  having  teeth  on  its  face  which  mesh  with  the 
elevating  worm.  The  rack  is  of  sufficient  length  to  provide  for  ele- 
vations from  0°  to  90°. 

The  cradle  is  bored  and  bushed  to  receive  the  gun.  Front  and  rear 
liners  are  provided  through  which  the  gun  slides  in  recoil.  In  addi- 
tion, the  cradle  forms  the  housing  for  the  recoil  and  counterrecoil 
systems.  The  interior  of  the  cradle  has  a  cored  recess  to  suit  the 
firing  mechanism. 

Recoil  mechanism  is  of  the  hydrospring  type.  The  recoil  cylinder 
is  screwed  from  the  front  into  a  seat  provided  in  the  top  of  the  cradle. 
The  piston  rod  is  attached  to  the  gun  lug  at  one  end  and  provided 
at  the  other  end  with  a  piston,  slightly  smaller  than  the  bore  of  the 
cylinder.  Three  longitudinal  throttling  grooves  are  cut  in  the  in- 
terior surface  of  the  recoil  cylinder,  each  groove  subtending  an  arc 
of  30°.  With  the  cylinder  in  assembled  position  one  groove  is  located 
at  the  bottom.  The  recoil  cylinder  has  a  capacity  of  6£  pints  of 
hydroline  oil. 

Two  cylindrical  holes  bored  in  the  cradle  form  the  housing  for  the 
counterrecoil  springs.  Spring  rods  are  attached  at  one  end  to  the 
gun  lug  and  at  the  other  end  to  the  spring-rod  piston.  When  the 
spring  compressor  is  first  assembled  it  is  secured  against  rotation  by 
a  retaining  screw.  The  counterrecoil  plunger,  designed  to  check  the 
recoiling  parts  as  they  return  to  battery,  passes  through  the  front 
end  of  the  recoil  cylinder  and  enters  the  recess  in  the  forward  end  of 
the  piston  rod. 

When  the  gun  is  fired  it  recoils  to  the  rear  about  12  inches  in  the 
cradle,  carrying  with  it  the  recoil  piston  and  spring  rods,  thereby 
compressing  the  counterrecoil  springs.  A  portion  of  the  energy  of 
recoil  is  taken  up  by  the  resistance  the  liquid  offers  to  being  forced 
through  the  variable  slots  formed  by  the  throttling  grooves  and  the 
constant  clearances  between  the  piston  head  and  the  interior  surface 
of  the  cylindrical  bore,  the  remainder  of  the  energy  being  absorbed 
by  the  springs.  The  width  of  the  grooves  is  uniform,  but  their  depth 
is  proportioned  so  that  the  areas  of  the  orifices,  varying  with  the 
position  of  the  piston  during  recoil,  will  be  such  as  to  give,  with  the 
aid  of  the  counterrecoil  springs,  a  constant  resistance  throughout  the 
length  of  recoil.  The  pressure  in  the  cylinder  is  therefore  a  uni- 
formly decreasing  one. 

The  counterrecoil  buffer  is  tapered  so  that  the  escape  of  oil  during 
xxmnterrecoil,  through  the  varying  diametrical  clearances  between 


374 

the  plunger  and  the  hole  in  the  piston,  will  offer  such  resistance  as 
will  control  the  motion  of  the  gun  during  its  return  to  battery  posi- 
tion after  firing. 

TJu'  -firing  mechanism  consists  of  a  firing  handle  whose  shaft  passes 
through  the  center  of  the  right  trunnion  and  carries  on  its  inner 
end  a  lever  which  operates  the  firing  shaft.  Previous  to  the  firing 
the  gunner  pulls  the  firing  handle  which  compresses  the  cocking 
spring  solid  and  moves  the  lever  on  the  breech  to  the  tripping  posi- 
tion; the  gunner  will  know  when  the  mechanism  has  reached  this 
position  by  feeling  the  increased  pressure  exerted  by  the  firing  spring. 
To  fire  the  gun,  the  gunner  pulls  the  firing  handle,  compressing  the 
firing  spring,  thus  tripping  the  firing  pin.  The  two-stage  movement 
of  the  firing  handle  is  intended  to  permit  a  shorter  movement  at  the 
moment  of  firing. 

The  illuminating  circuit  has  a  360°  contact  mounted  in  the  base 
plate.  Direct-current  mains  of  either  110  or  220  volts  are  connected 
with  an  outlet  box  located  in  the  concrete  emplacement. 

Two  circuits  are  led  from  the  360°  contact,  one  leading  to  the  plug 
box  of  a  portable  lamp  of  line  voltage,  and  the  other  circuit  lead- 
ing to  the  switch  box;  from  here  it  is  led  to  the  rheostat,  from 
which  two  branch  feeders  are  taken  to  the  two  receptacle  boxes 
bolted  to  the  yoke.  A  circuit  is  taken  from  the  right  receptacle  box 
with  a  spliced  branch  feeder  to  a  candelabra  receptacle  for  the  reti- 
cule lamp  and  deflection  pointer  lamp.  Another  circuit  is  run  from 
the  left  receptacle  box  with  two  spliced  branch  feeders  to  a  cande- 
labra receptacle  for  the  elevation  pointer,  range  disk  pointer,  and 
elevation  correction  lamps.  These  lamps  are  supported  by  lamp 
brackets  fastened  to  the  trunnion  and  sight  mechanism. 

The  rheostat  used  cuts  down  the  voltage  and  makes  the  use  of 
low-voltage  lamps  and  batteries  practicable  in  case  the  line  voltage 
fails  through  accident. 

The  cable  leading  from  the  360°  contact  with  the  plug,  switch,  and 
rheostat  is  of  the  twin  conductor,  leaded,  and  armored  type.  The 
two  branch  feeders  leading  from  the  rheostat  to  the  receptacle  boxes 
and  thence  to  the  lamp  brackets  are  of  the  portable  conductor  type. 
The  various  cables  are  fastened  to  the  mount  by  means  of  cable 
straps  and  twisted  hooks. 

Sight  for  antiaircraft  mount,  model  of  1917. — This  instrument 
includes  all  parts  used  to  direct  the  elevating  and  traversing  of  mount 
so  that  the  gun  may  be  pointed  properly  in  elevation  and  direction. 
The  parts  consist  of  a  sight  proper  (telescope) ,  the  sight  mount,  range 
disk,  correction  scale,  and  pointer.  For  any  visible  target  the  data 
necessary  to  properly  lay  the  gun  consist  of  fuse-setter  range,  travel 
in  elevation  and  deflection,  and  the  required  arbitrary  correction. 


375 

The  target  is  brought  into  the  field  of  view  by  turning  the  azimuth 
and  the  angle-of-sight  knobs,  imparting  to  the  sight  a  movement  in 
azimuth  and  elevation,  respectively. 

A  scale  is  provided  whereby  the  sight  proper  may  be  set  in  eleva- 
tion at  any  desired  angle,  whence  the  gun  by  means  of  the  elevating 
mechanism  is  also  elevated  to  the  same  angle  (corrections  being  zero). 

An  azimuth  scale  is  also  provided  between  the  fixed  and  rotating 
parts  of  the  carriage  so  that  the  gun  by  means  of  the  traversing 
mechanism  may  be  set  at  any  desired  angle  in  azimuth. 


376 


CD 


75-MILLIMETER  ANTIAIRCRAFT  TRUCK  MOUNT,  MODEL 

OF  1917. 


To  appreciate  the  difficulty  of  antiaircraft  fire  it  suffices  to  con- 
sider that  one  is  firing  practically  at  a  bird  whose  velocity  is  about 
50  meters  per  second,  i.  e.,  one-sixth  the  average  velocity  of  the 
projectile  itself  in  the  case  of  the  75 -millimeter  field  gun.  The 
principal  result  hoped  for  by  the  antiaircraft  artillery  fire  is  to  pre- 
vent airplanes  from  accomplishing  their  mission  by  obliging  them  to 
fly  at  increasing  altitudes,  to  continually  change  their  direction,  and 
also  to  prevent  their  crossing  certain  regions. 

At  the  present  time  the  antiaircraft  artillery  aims  to  keep  air- 
planes beyond  the  limit  of  their  range.  Observation  airplanes  are 
obliged  to  fly  out  of  range,  reconnoitering  airplanes  continually  in- 
crease the  height  at  which  they  cross  the  lines,  and  battle  planes  must 


TRUCK  IN  TRAVELING  POSITION    (RIGHT-SIDE  VIEW). 

also  fly  very  high,  except  when  they  wish  to  attack  trenches  or  bat- 
teries with  machine  guns.  Raids  of  this  kind  are  almost  exclusively 
carried  on  at  night.  The  result  is  that  three  kinds  of  fire  have 
become  particularly  important: 

Fire  against  airplanes  at  a  great  range  and  a  great  height. 

Fire  against  very  speedy  airplanes  attacking  positions. 

Fire  at  night  against  bombarding  airplanes. 

The  necessity  of  extemporizing  an  antiaircraft  weapon  to  meet  the 
above  requirements  led  to  the  design  of  the  75-millimeter  antiair- 

(377) 


378 

craft  truck  mount.  This  development  involved  the  use  of  the  Ameri- 
can model  1916  field  gun  and  recoil  mechanism,  which  was  most 
available.  This  gun  and  recoil  mechanism  is  secured  on  an  offset 
swivel  gun  mount,  suitably  mounted  on  a  2^-ton  White  gasoline- 
driven  truck,  Model  TBC,  designed  to  receive  the  base  plate  of  the 
top  carriage. 

The  gun  (see  p.  75)  is  carried  on  a  cradle  which  rocks  in  elevation 
about  the  trunnions  of  the  top  carriage,  and  by  means  of  the  elevat- 


75M.M.  ANTI-AIRCRAFT 
TRUCK  MOUNT,  MODEL  OF  1917 
SIDE  ELEVATION. 


e         6  g     it     n    go 


tr    fi    to    «4    e» 


ing  mechanism  a  range  of  elevation  from  31°  to  82°  is  obtainable. 
The  piece  has  a  recoil  of  33  inches  on  its  cradle  and  is  provided  with 
a  recoil  cylinder,  counterrecoil  springs,  and  buffer. 

The  piece  has  a  muzzle  velocity  of  1,830  feet  per  second,  and  uses 
high-explosive  and  shrapnel  shells,  the  former  weighing  14.7  pounds 
and  the  latter  14.3  pounds,  employing  a  20-second  (maximum)  time 
fuze  with  each.  With  a  maximum  vertical  elevation  of  82°  a  ver- 
tical bursting  ordinate  of  5.980  meters  is  obtained,  and  with  the 


379 

minimum  elevation  of  31°  a  vertical  bursting  ordinate  of  1,750 
meters  is  obtained.  In  both  cases  the  bursting  ordinates  were 
limited  by  the  time  fuze. 

The  gun  with  the  breech  is  located  directly  behind  the  driver's 
seat,  but  as  the  length  of  recoil  is  fixed,  the  firing  position  is  limited 
to  such  horizontal  position  of  the  mount  as  would  permit  of  the  gun 
recoil  clearing  the  sides  or  rear  of  the  truck  chassis. 


HON. 


A  heavy  base  plate  is  secured  to  the  rear  end  of  the  chassis,  and 
the  top  carriage  swings  in  azimuth  about  a  central  pintle  bolt  on 
rollers.  By  means  of  the  traversing  mechanism,  the  carriage, 
carrying  the  gun  and  its  corresponding  mechanism,  can  be  traversed 
through  240°,  which  is  the  field  of  fire.  The  chassis  is  equipped  with 
firing  and  stability  jacks  to  relieve  the  rear  springs  and  truck  of  all 
firing  strains.  With  the  jacks  properly  placed  and  leveled,  the 
vehicle  is  supported  on  a  rigid  horizontal  platform  formed  by  the 
firing  jacks  and  the  base  plate.  When  in  action  the  stability  equip- 
ment functions  to  prevent  the  mount  from  overturning  when  the 
gun  is  fired  at  low  angles  of  elevation. 

Weights,  dimensions,  and  ballistics. 

Caliber    inches.-  2.  953 

Total  length  of  gun do 90.9 

Length  of  the  rifled  portion  of  the  bore do 72.  72 

Length  in  calibers 28.4 

Weight  of  projectile : 

Shell pounds__  14.7 

Shrapnel do 14.3 

Weight  of  full  powder  charge do 1.625 

Service  muzzle  velocity feet  per  second 1,830 

Horizontal  range  at  45°  elevation  (14.3-pound  shell) __yards__  10,595 

Maximum    elevation degrees 82 

Minimum   elevation do 31 

Total  traverse..                                                                                  __do__  240 


380 

Weight  of  gun  and  breech  mechanism pounds—  750 

Weight  of  gun,  breech  mechanism,  and  carriage do 3,300 

Weight  of  chassis,  including  attachments  and  accessories do 4.  500 

Weight  of  chassis  only  (without  attachments) do 4,100 

Weight  of  top  carriage,  and  its  corresponding  mechanism,  etc do 4,  250 

Total  traveling  weight  of  unit  (fully  equipped) do 9,  500 

Over-all  length  of  vehicle  (traveling  position) . inches__  209 

Over-all  width  of  vehicle  (traveling  position) do 74$ 

Wheel  base - do I57i 

Wheels,   front do 36  x  4 

Wheels,    rear do 36  x7 

Road  clearance do 9$ 

Rating  of  load tons—  2$ 

Tread  inches--  62 

The  principal  parts  of  the  carriage  are:  The  base  plate,  top  car- 
riage, recoil  mechanisms,  cradle,  elevating  and  traversing  mecha- 
nism, angle  of  sight  mechanism,  firing  jacks,  stability  jacks,  and 
rails. 

The  Ixise  plate  is  a  rectangular  steel  casting  secured  to  the  truck 
chassis,  and  serves  as  a  support  for  the  top  carriage.  The  traverse 
of  the  top  carriage  is  limited  by  lugs  provided  on  the  top  of  the  clip 
surface.  The  clip  prevents  the  traversing  rollers  from  leaving  their 
path  due  to  the  shock  caused  by  action  of  recoil  or  counter  recoil. 
Four  lugs  radiating  from  the  pintle  bearing  serve  as  points  of  at- 
tachment for  the  firing  jacks  and  rail  tie-rods.  At  the  forward  end 
of  the  base  plate  are  two  lugs,  one  on  either  side,  which  project  out 
at  right  angles  to  the  truck  chassis,  serving  as  points  of  attachments 
for  the  stability  jacks.  The  firing  strains  produced  during  action 
are  transmitted  through  these  lugs  and  jacks,  thus  eliminating  all 
unnecessary  strains  from  the  rear  springs  and  wheels  of  the  truck. 

The  top  carriage  is  a  steel  casting,  comprising  a  base  and  two  verti- 
cal side  frames  designed  to  mount  the  cradle  to  permit  sufficient  clear- 
ance for  the  recoiling  parts  at  high  angles  of  fire.  A  pintle  bolt  pro- 
jecting from  the  base  plate  through  the  case  of  the  top  carriage 
forms  an  axis  about  which  the  carriage  is  rotated  in  azimuth  upon 
four  rollers  resting  on  the  roller  path  of  the  base  plate.  Between 
the  two  side  frames  is  housed  the  angle  of  sight  mechanism.  The 
traverse  of  the  carriage  is  limited  to  240°  by  means  of  a  traversing 
stop  plunger,  which  engages  the  lugs  on  the  clip  surface.  When  pre- 
paring for  travel  the  stop  plunger  can  be  raised  to  clear  the  limit  stop, 
thus  permitting  the  proper  position  of  carriage  when  en  route.  Four 
seats  (two  on  each  side)  riveted  to  swinging  arms,  for  the  use  of  the 
cannoneers  during  action,  are  secured  to  the  top  carriage. 

Recoil  mechanism. — The  recoil  mechanism  is  of  the  hydrospring 
type,  with  recoil  cylinder  mounted  above  the  gun.  Three  longitudi- 
nal ribs,  or  throttling  bars,  of  uniform  width  but  varying  height,  are 


formed  on  the  inside  of  the  cylinder  and  engage  with  corresponding 
grooves  in  the  piston  head.  The  clearance  between  the  bars  and 
grooves  determines  the  amount  of  oil  which  may  pass  from  the  back 
to  the  front  of  the  piston  head,  thereby  regulating  the  amount  of 
recoil. 

The  piston  rod  is  a  hollow  steel  tube  and  is  fitted  with  a  bronze 
head.  The  rear  end  of  the  piston  rod  is  bored  out  to  accommodate 
the  counterrecoil  buffer,  which  fits  into  the  bore  with  a  small  clear- 
ance. This  clearance  depends  on  the  taper  of  the  buffer,  as  the  hole 
in  the  piston  rod  is  of  constant  diameter. 

In  each  spring  cylinder,  three  coils  of  inner  and  outer  counterrecoil 
springs  are  assembled  over  the  spring  rod.  The  inner  and  outer 
springs  are  wound  in  opposite  directions  to  prevent  nesting,  and  each 
pair  of  inner  springs  is  separated  from  the  next  pair  by  a  bronze 
separator. 

When  fired  the  gun  moves  back  on  its  slides,  carrying  with  it  the 
recoil  cylinder  and  counterrecoil  springs.  The  piston  rod  is  secured 
to  a  nonrecoiling  part  of  the  carriage ;  thus,  when  the  recoil  cylinder 
moves  to  the  rear  the  oil  in  it  must  pass  from  one  side  of  the  piston  to 
the  other.  The  energy  of  recoil  of  the  gun  is  absorbed  by  the  resist- 
ance which  the  oil  offers  to  being  forced  through  small  openings  past 
the  piston,  also  by  the  compression  of  the  counterrecoil  springs.  The 
energy  stored  up  by  the  springs  returns  the  gun  to  battery  position. 
The  return  movement  is  eased  and  regulated  by  the  counterrecoil 
buffer,  which  prevents  any  undue  shock  to  the  recoiling  parts  by 
offering  resistance,  due  to  the  fluid  in  the  hole  of  the  piston  rod  being 
forced  out  as  the  buffer  gradually  enters  the  hole. 

The  cradle  comprises  the  counterrecoil  spring  cylinders  with  their 
component  attached  parts.  The  spring  cylinders  are  below  the  gun 
and  in  the  form  of  two  cylinders  joined  at  the  center.  Above  the 
cylinders  are  the  bronze  lined  gun  ways  or  slides.  The  trunnions  are 
secured  to  the  cylinders,  and  the  elevating  arc  is  bolted  to  lugs  on  the 
bottom.  Riveted  to  the  right  side  of  the  cradle  is  the  elevation  stop 
and  the  depression  stop. 

The  rocker,  a  U-shaped  forging,  is  journaled  upon  the  trunnions. 
Bearings  are  provided  in  the  bottom  of  the  rocker  for  the  elevating 
mechanism  and  a  rack  is  cut  on  the  exterior  of  its  yoke  for  the  angle 
of  sight  worm. 

The  traveling  lock  is  located  under  the  rear  end  of  the  spring 
cylinder.  This  device  functions  to  lock  the  cradle  at  an  angle  of 
approximately  32°  in  elevation  when  preparing  for  travel,  thus 
the  elevating,  angle  of  site,  and  traversing  mechanisms  are  relieved 
of  all  unnecessary  vibrations  when  the  vehicle  is  en  route.  At  the 
front  end  of  the  base  plate  is  hinged  a  lock  bar  and  brace,  which 


382 

engage  a  lug  provided  on  the  rear  end  of  the  cradle.    In  order  to 
bring  this  lug  in  proper  position  to  receive  the  lock  bar  the  cradle 


GUN  MOUNT   SHOWING  GUN  AT  MAXIMUM  ELEVATION. 

must  be  traversed  to  its  traveling  position;  that  is,  to  bring  the 
axis  of  the  gun  into  a  vertical  plane  with  the  center  line  of  the 
truck  chassis. 


383 

The  elevating  mechanism  consists  of  an  elevating  worm,  an  elevat- 
ing arc  or  rack,  and  a  train  of  miter  gears  mounted  on  the  right  side 
of  the  rocker.  The  shaft  on  which  the  elevating  handwheel  is 
mounted  extends  through  the  side  frame  of  the  top  carriage. 

The  worm  is  operated  through  gears  and  a  shaft  by  means  of  a 
handwheel,  and  rotates  the  cradle  about  the  trunnions.  Any  move- 
ment imparted  to  the  worm  by  the  handwheel  will  cause  the  cradle 
to  move  with  relation  to  the  top  carriage.  One  turn  of  the  hand- 
wheel  will  cause  the  gun  to  be  elevated  or  depressed  approximately 
1.7°.  The  elevating  arc  permits  a  change  of  elevation  from  31°  mini- 
mum to  82°  maximum. 


TRUCK   IN   TRAVELING   POSITION    (LEFT    SIDE   VIEW). 

The  traversing  mechanism  located  on  the  left  side  of  the  top  carriage, 
consists  mainly  of  a  traversing  handwheel  and  shaft,  worm,  worm 
wheel,  clutch,  bevel  pinion,  traversing  pinion,  and  rack.  The  worm 
engages  the  worm  wheel  and  can  be  either  engaged  with  or  disen- 
gaged from  the  shaft  by  means  of  a  clutch  operated  by  a  foot  lever. 
If  the  clutch  be  disengaged,  the  worm  and  worm  wheel  are  released 
from  the  gear  train,  and  the  top  carriage  may  be  traversed  about  the 
pintle  bolt  by  hand.  The  traversing  pinion  engages  the  traversing 
rack  which  is  secured  to  the  base  plate.  One  turn  of  the  handwheel 
will  cause  the  gun  to  be  traversed  approximately  2°. 

The  angle  of  site  mechanism  consists  of  a  handwheel,  handwheel 
shaft,  and  angle  of  site  worm.  The  angle  of  site  worm  is  secured 
to  the  top  carriage  and  engages  in  a  rack  cut  in  the  face  of  the  yoke  of 
the  rocker.  To  one  end  of  the  shaft  which  extends  out  to  the  right 
side  of  the  top  carriage  is  secured  the  handwheel  and  to  the  other  end 
is  fixed  a  miter  gear. 
55160—21 25 


384 

The  angle  of  site  worm  is  a  one-piece  forging  comprising  a  worm, 
a  shaft,  and  a  miter  gear  of  the  same  size  as  that  on  the  bracket  at 
an  angle  of  90°  to  the  handwheel  shaft  and  with  the  miter  gears  at 
the  ends  in  mesh.  One  turn  of  the  handwheel  will  cause  the  rocker 
and  the  cradle  to  be  elevated  or  depressed  approximately  25  mils. 
The  rocker  allows  a  correction  of  124  mils  depression  and  200  mils 
elevation. 

Firing  and  stability  jacks. — The  principal  parts  of  the  firing 
jacks  are  the  jack  body,  jack  screw,  foot,  and  spade.  There  are  two 
firing  jacks,  the  bodies  being  hinged  at  the  rear  corners  of  the  base 
plate  as  shown  on  page  385.  At  the  end  of  the  jack  screw  the  foot,  or 
float,  is  secured  by  a  ball  joint,  which  enables  the  jack  to  be  seated  on 
inclined  surfaces.  The  foot  is  provided  with  a  sharp-pointed  spade, 
which  is  driven  into  the  ground.  A  tie  rod  is  used  between  the  two 
jacks  to  keep  the  jack  bodies  from  spreading  out  when  the  load  is 
put  on  the  screws.  The  firing  jacks  act  as  rigid  supports  for  the  base 
plate  at  the  rear  corners,  and  relieve  the  truck  chassis  of  firing  strains. 

The  stability  jacks  are  essentially  the  same  in  construction  as  the 
firing  jacks,  but  heavier.  Their  function  is  to  prevent  the  overturn- 
ing of  the  truck  when  the  gun  is  fired  at  low  angles  of  elevation,  and 
also  to  take  the  firing  strains.  The  stability  jacks  are  hinged  to  the 
base  plate,  one  on  each  side,  and  each  is  supported  by  a  strut  hinged 
in  a  lug  secured  to  the  truck  chassis.  The  stability  jack  floats  are 
provided  with  spades. 

When  the  carriage  is  in  the  traveling  position  the  firing  jacks  and 
stability  jacks  are  folded  up  and  secured  by  chains.  The  spades  are 
removed  and  placed  in  receptacles  provided  on  the  chassis.  The 
stability  jack  struts  are  unpinned  from  the  forward  lugs,  removed, 
and  carried  in  holders  on  the  base  plate.  The  tie  rods  are  folded  with 
the  jacks  and  chained  in  position. 

Two  stability  rails  and  tie  rods  are  provided  with  each  mount,  one 
being  straight  and  the  other  having  an  offset.  They  are  crossed 
under  the  rear  axle  of  the  truck,  the  rear  ends  being  located  so  that 
the  firing  jack  floats  set  in  the  spaces  between  the  angles  of.each  rail. 
The  middle  angles  at  the  front  ends  of  the  stability  rails  are  attached 
to  the  stability  rail  tie  rods,  which  in  turn  are  connected  to  the 
adapters  on  the  lugs,  directly  opposite  the  firing  jack  lugs,  on  the 
base  plate. 

When  the  vehicle  is  to  be  emplaced,  both  of  the  truck  wedges  are 
placed  on  the  ground  with  the  channel  side  up,  and  the  front  wheels 
of  the  truck  are  run  up  the  channels  between  the  flanges.  The  pur- 
pose of  these  wedges  is  to  raise  the  front  end  of  the  truck  so  that  the 
mount  will  be  level  when  the  rear  end  is  jacked  up.  Two  steel  blocks 
are  provided  for  blocking  the  front  wheels  when  they  are  run  up  on 
the  truck  wedges. 


385 

Rear  axle  slings. — When  traveling,  the  slings  hang  loosely  under 
the  truck,  one  on  either  side  of  the  transmission.  The  front  ends 
of  the  slings  are  looped  around  through  holes  in  the  base  plate  and 
clamped  in  place  permanently.  Two  steel  rods  are  inserted  in  the 
rear  loops  of  the  slings  and  placed  across  the  rear  end  of  the  chassis 
when  the  mount  is  emplaced,  and  two  pieces  of  pipe  are  inserted 
in  the  front  loops  of  the  slings  and  placed  across  the  ribs  on  the 
front  end  of  the  base  plate.  The  purpose  of  these  slings  is  to  keep 


FIRING  AND   STABILITY  JACKS. 

the  rear  springs  compressed  and  the  rear  wheels  off  the  ground 
when  the  mount  is  jacked  up. 

The  electrical  equipment  consists  of  five  lamps  receiving  current 
from  a  storage  battery,  suitable  wiring,  and  switching  arrangements. 

Two  three-cell,  6  to  8  volt  batteries  are  provided,  one  for  reserve, 
each  of  120-ampere-hour  capacity,  and  are  carried  in  a  metal  con- 
tainer which  is  bolted  to  the  chassis  of  the  truck.  One  battery,  when 
fully  charged  and  in  good  condition,  will  furnish  energy  for  about 
24  hours'  continuous  service  for  all  lamps. 


386 

All  wiring  is  permanent  and  the  connecting  wires  are 
by  steel  armor  wherever  mechanical  injury  is  likely.  Should  it  be 
necessary  to  remove  the  top  carriage,  the  lead  from  the  battery 
which  runs  through  the  pintle  bolt  may  be  disconnected  above  the 
top  of  the  bolt  by  unwrapping  the  insulation  and  opening  the  con- 
necting plug  there  provided. 

The  lamps  are  specially  designed  to  withstand  the  shock  of  firing 
and  are  rated  at  2  candlepower.  One  lamp  is  provided  for  illumi- 
nating each  of  the  following  parts: 

Deflection  correction  pointer. 

Reticule. 

Elevation  pointer. 

Range  disk  pointer. 
,  Elevation  correction  pointer. 


TRUCK   MOUNT   IN   BATTERY    POSITION. 

A  snap  switch  is  provided  in  the  main  battery  lead  which  controls 
all  the  lamps,  and  the  lamps  should  be  disconnected  by  means  of  this 
switch  when  not  in  use. 

The  sight  for  this  antiaircraft  vehicle  is  an  instrument  which  in- 
cludes all  parts  used  to  direct  the  elevating  and  traversing  of  the 
mount  so  that  the  gun  may  be  pointed  properly  in  elevation  and 
azimuth.  The  parts  consist  of  a  sight  proper  (telescope),  the  sight 
mount,  range  disk,  correction  scale,  and  pointer.  For  any  visible 
target,  the  data  necessary  to  properly  lay  the  gun  consist  of  fuze 
setter  range,  travel  in  elevation  and  deflection,  and  any  desired 
arbitrary  correction. 

The  object  is  brought  into  the  field  of  view  by  turning  the  azimuth 
and  the  angle  of  site  knobs,  imparting  thereby  to  the  sight  a  move- 
ment in  azimuth  and  elevation,  respectively.  The  object  is  followed 
by  continuing  the  movement  of  these  knobs.  Detailed  description 
of  the  model  1917  antiaircraft  sight  may  be  found  in  separate  pam- 
phlet covering  fire-control  instruments. 


GUN  AND  HOWITZER  MOTOR  CARRIAGES. 


The  idea  of  mounting  guns  and  howitzers  on  carriages  equipped 
with  motors  for  propelling  the  carriages  originated  during  the  war 
in  the  United  States  and  France,  and,  curiously  enough,  was  con- 
ceived independently  at  the  same  time  in  both  countries.  In  the 
United  States  motor  carriages  were  first  made  in  an  effort  to  pro- 
duce a  transport  vehicle  which  would  provide  a  faster  means  for 


105-MM.  HOWITZER  MOTOR  CARRIAGE,  MODEL  OF  1920. 

transporting  guns  from  place  to  place.  In  France  the  motor  carriage 
was  developed  from  a  tank  equipped  with  a  75-millimeter  gun.  It 
is  interesting  to  note  that  in  France  during  the  war  a  motor  carriage 
mounting  a  220-millimeter  howitzer  while  carrying  out  a  series  of 
maneuvering  tests  was  actually  engaged  in  warfare. 

In  the  United  States  during  and  since  the  war  a  number  of  experi- 
mental types  of  motor  carriages  have  been  built  for  various  caliber 

(387) 


388 


guns  and  howitzers  from  the  75-millimeter  gun  to  the  240-millimeter 
howitzer.  Two  types  of  carriages  for  the  155-millimeter  gun  having 
widely  different  characteristics  have  been  issued  to  the  service  for 
field  tests. 

The  relative  advantages  and  disadvantages  of  tractor-drawn  ar- 
tillery and  of  motor  carriages  are  many,  and  for  the  most  part  are 
apparent,  since  there  is  but  a  limited  amount  of  data  available  upon 
which  to  base  a  comparison. 

The  mechanical  characteristics  of  the  motor  carriages  permit  of 
certain  advantages  over  existing  types  of  artillery,  namely,  higher 
speed  on  good  roads;  ability  to  go  anywhere  off  of  roads;  ability  to 


SELF-PROPELLED  WHEELED  MOUNT,  FOR  3-INCH  ANTIAIRCRAFT  GUN  MOUNT. 

cross  streams  even  when  fully  submerged;  all-around  fire;  better 
stability  when  firing;  firing  immediately  upon  reaching  battery 
position. 

Motor  carriages  are  divided  into  three  general  classes,  as  follows : 

1.  Wheel  type. 

2.  Track-laying  or  "  caterpillar  "  type. 

3.  Combined  wheel  and  track-laying  type. 

The  wheel  type  has  limited  application,  since  its  use  is  restricted 
to  good  roads  or  around  fortified  places  for  antiaircraft  use  where 
good  roads  are  available.  A  few  of  this  type  have  been  constructed 
for  experimental  purposes. 


389 

The  track-laying  type,  or  caterpillar  type,  to  use  its  trade  name, 
has  a  track  construction  similar  to  the  ordinary  tractor.  Most  of 
the  experimental  types  built  in  this  country  and  in  France  have  been 
of  this  type.  With  this  type  the  track-supporting  members  may  be 
sprung  or  rigidly  mounted  similar  to  the  large  tank  construction. 
For  divisional  artillery  this  type  must  be  capable  of  high  speed  on 
good  roads.  It  is  always  operated  as  a  track-laying  vehicle. 

The  combined  wheel  and  track-laying  type  may  be  operated  on 
wheels  similar  to  any  wheeled  vehicle  when  roads  permit,  or  may  be 
operated  on  a  track  which  passes  over  the  wheels  and  is  driven  by 
the  power  wheel.  Obviously  this  type  has  certain  advantages,  since 
it  can  be  operated  either  as  a  wheeled  vehicle  or  as  a  track-laying 
vehicle. 

The  following  description  applies  to  two  types  of  motor  carriages 
that  have  recently  been  issued  to  the  service : 

The  engine  is  lubricated  by  the  splash  system.  The  gasoline 
system  consists  of  a  30-gallon  fuel  tank,  from  which  gasoline  is 
supplied  to  the  carbureter  on  the  engine  by  means  of  a  vacuum 
tank.  The  engine  is  started  by  means  of  a  hand  starter  on  the 
left  side  of  the  vehicle.  The  flywheel  of  the  engine  is  also  the 
main  clutch  by  which  power  is  transmitted  from  the  engine  to 
the  transmission.  The  vehicle  is  mounted  with  double  solid-tire 
wheels  41  inches  in  diameter  by  10  inches  base.  Each  wheel  is 
mounted  on  a  single  annular  ball  race,  and  each  driving  wheel  is 
equipped  with  an  internal  gear  for  driving  purposes. 

The  transmission  case  and  engine  crankcase  are  integral.  The 
transmission  consists  of  a  progressive  change  gear  set  with  its 
shafts  parallel  to  the  engine  crankshaft.  It  is  driven  by  one  of 
its  gears  meshing  with  a  gear  on  the  driven  part  of  the  engine 
clutch.  Power  is  transmitted  from  the  transmission  to  the  front 
wheels  by  a  roller  chain  which  drives  the  front  wheel  pinion  shaft. 
Power  is  transmitted  to  the  rear  wheels  by  a  chain  from  the  front 
wheel  pinion  shaft  to  a  jack  shaft  through  a  set  of  bevel  gears  and 
shaft  on  the  left  side  of  the  vehicle  to  a  jack  shaft  behind  the  gun 
fastening,  and  thence  to  the  rear  wheel  pinion  shaft  by  another 
roller  chain.  Both  front  and  rear  pinion  shafts  are  provided  with 
a  differential. 

The  gear  set  of  the  transmission  has  three  speeds  forward  and 
three  speeds  reverse,  giving  a  range  of  speed  from  2  miles  per 
hour  to  15  miles  per  hour  on  forward  or  reverse  motion. 

The  control  group  consists  of  a  steering  wheel  which  operates 
the  front  wheels,  a  change  gear  lever,  a  forward  and  reverse  lever, 
a  hand  brake  lever,  a  brake  foot  pedal,  a  clutch  foot  pedal,  and  a 
foot  accelerator  for  throttle  control. 


SELF-PROPELLED  WHEELED  MOUNT  FOR  3-INCH  ANTI- 
AIRCRAFT GUN,  MODEL  OF  1917. 


This  motor  carriage  represents  one  of  the  first  efforts  made  in  the 
United  States  to  mount  cannon  on  a  vehicle  of  the  self-propelled  type. 

They  were  designed  during  the  war  in  an  effort  to  produce  a  vehicle 
which  would  serve  as  a  transport  vehicle  for  cannon  over  good  roads. 
While  the  vehicle  was  given  the  designation  of  an  antiaircraft  car- 
riage, its  limitations  for  this  service  were  soon  discovered,  and 
because  of  these  limitations,  chief  among  which  were  its  great  weight 
in  proportion  to  the  power  of  the  gun  mounted  upon  it  and  its 
dependence  upon  good  roads,  it  was  not  considered  acceptable  for 
use  under  field  conditions. 

This  vehicle  was  designed  especially  to  mount  a  "  3-inch  antiair- 
craft gun,  model  of  1917,"  described  in  detail  on  page  363. 


LEFT-SIDE  VIEW  OF  MOUNT  IN  TRAVELING  POSITION. 

The  various  units  comprising  the  vehicle  are  assembled  on  a  main 
frame.  This  frame  is  of  a  built-up  construction  and  is  arranged, 
between  the  front  and  rear  wheels,  to  take  the  3-inch  antiaircraft 
mount  and  to  give  360°  traverse.  That  part  of  the  frame  between 
the  front  and  rear  wheels  is  provided  with  four  outriggers,  which 
can  be  folded  up  out  of  the  way  in  traveling.  The  front  and  rear 
of  the  vehicle  are  provided  with  stabilizers,  which  can  T?e  screwed 
down  on  floats  placed  on  the  ground  when  the  vehicle  is  in  firing 
position. 

Power  for  propelling  the  vehicle  is  furnished  by  a  4-cylinder  4-cycle 
T-head  gasoline  engine,  which  develops  60  horsepower  at  1,200  revo- 
lutions per  minute.  The  engine  is  located  transversely  at  the  front 

(390) 


391 

end  of  the  vehicle,  the  entire  power  plant,  including  the  engine,  trans- 
mission, and  radiator,  overhanging.  Two  radiators  are  mounted  in 
tandem  and  are  cooled  by  a  chain-driven  fan. 

A  hand-brake  lever  for  the  two  rear  wheels  is  located  at  the  rear 
part  of  the  carriage  and  is  used  only  during  firing  or  in  extreme 
cases  while  traveling.  The  instrument  board  has  on  it  a  speedometer 
and  an  ignition  switch. 

The  general  weights  and  characteristics  are  as  follows: 

Total  weight  in  working  order pounds 31,720 

Weight  on   front  wheels do 17,680 

Weight  on  rear  wheels do 14,040 

Maximum  over-all  length  of  vehicle inches__  276 

Maximum  over-all  height  of  vehicle do 102 

Maximum  over-all  width  of  vehicle do 101 

Maximum  over-all  width  with  outriggers  in  place do 174 

Length  of  wheel  base do 157 

Diameter  of  wheels  over  tires do 41 

Width  of  double  tires do 10 

Distance  from  center  to  center  of  wheels  or  gauge do 85 

Maximum  road  speed,  miles  per  hour 15 

Bore  and  stroke  of  motor inches 5$  x  7 

Type  of  motor  :  4  cylinder,  ball-bearing  crankshaft,  horsepower 60 

Number  of  speeds  forward 3 

Number  of  speeds  reverse 1 

Capacity  of  fuel  tank gallons 30 

Type  of  vehicle  drive 4-wheel 

Angle  of  gun  elevation 0°  to  85° 

Traverse  of  gun  mount 360° 

Turning  radius  of  vehicle feet 40 

For  additional  information  see  page  363. 


SELF-PROPELLED  CATERPILLAR,  MARK  II,  FOR  155-MIL- 
LIMETER GUN  (FILLOUX),  MODEL  OF  1918. 


This  motor  carriage  is  a  self-propelled  road  vehicle  of  the  track- 
laying  type,  upon  which  is  mounted  the  155-millimeter  gun  (Filloux), 
model  of  1918. 

The  main  frame  is  a  steel,  box-section,  casting  to  which  all  of  the 
various  parts  of  the  chassis  and  gun  are  attached,  and  which  is  sup- 
ported on  the  roller  frames  of  the  track-laying  mechanism  by  several 


TRAVELING  POSITION    (PLAN   VIEW). 

sets  of  coil  springs,  an  equalizing  mechanism,  and  several  connecting 
and  alignment  links. 

Power  is  furnished  by  a  6-cylinder,  T-head,  4-cycle  "  Sterling " 
gasoline  engine,  which  develops  a  maximum  of  145  horsepower  at 
1,500  revolutions  per  minute.  The  engine  is  located  under  an  en- 
gine hood  on  the  front  part  of  the  frame  with  the  radiator  and  cool- 
ing fan.  Ignition  is  by  dry-cell  batteries  and  coil,  when  starting 

(392) 


393 

the  engine  and  by  a  high-tension,  two-spark  Berling  magneto  when 
operating.  The  gasoline  supply  system  consists  of  a  45-gallon  sup- 
ply tank,  a  Stewart  vacuum  tank,  and  a  Schebler  carbureter,  which 
is  attached  to  the  engine. 

The  engine  delivers  its  power  to  the  transmission  through  a  dry 
plate,  multiple  disc,  master  clutch.  The  front  transmission  consists 
of  a  selective  change  gear  set  and  two  steering  clutch  and  planetary 
brake  sets.  Power  from  these  is  conducted  through  a  propeller  shaft 
to  the  intermediate  and  final  drive  gears,  thence  to  the  driving 
sprocket,  at  the  rear  of  the  vehicle,  which  engages  the  track  links. 

The  track-laying  mechanism  consists  of  two  truck  frames  on  each 
side  of  the  main  frame,  an  endless  series  of  track  links  on  each  side, 
and  an  equalizing  mechanism.  The  truck  frames  support  the  frame 
through  springs  and  are  fitted  with  flanged  truck  wheels  which 
roll  on  the  rails  of  the  track  links.  The  front  roller  frames  carry 
the  front  idler  sprockets  and  support  the  frame  through  an  equalizer 
arrangement.  This  is  pivoted  at  the  front  end  of  the  main  frame, 
so  that  one  track,  in  passing  over  an  obstruction  rises,  relative  to  the 
main  frame  and  cause  the  opposite  side  to  be  pushed  down,  relative 
to  the  main  frame  on  to  firm  ground.  In  this  way  the  frame  is 
kept  on  an  even  keel  and  is  relieved  of  most  of  the  wearing  strains. 

The  track  links  consist  of  a  series  of  castings,  similar  to  chain 
links,  with  flat  plate  shoes  bearing  on  the  ground,  and  two  T-section 
rails,  which  are  connected  by  case-hardened  pins.  The  T-section 
rails  of  the  links  provide  a  set  of  rails  similar  to  a  railroad  track, 
upon  which  the  truck  wheels  roll.  The  thrust  of  the  sprocket 
driving  teeth  is  taken  upon  hardened  steel  bushings,  pressed  into 
one  end  of  the  track  links  over  the  track  connecting  pins.  The 
tracks  are  kept  at  their  proper  tension  by  means  of  a  tightening 
screw  on  the  idler  sprocket  axle  at  the  forward  end  of  the  front 
roller  frame. 

The  motor  carriage  is  operated  by  one  man.  The  controls  con- 
sist of  master  clutch  and  gear  shifting  hand  levers,  at  the  left  of 
the  operator;  a  brake  hand  lever  and  spark  and  throttle  levers 
on  the  control  support  in  front  of  the  operator,  a  steering  clutch 
and  planetary  brake  lever,  one  on  each  side  of  the  operator,  and 
two  brake  foot  pedals  for  use  in  either  stopping  or  steering  the 
mount. 

Steering  is  accomplished  by  means  of  a  lever  for  each  steering 
clutch  and  planetary  brake  set.  They  can  be  operated  separately 
or  together,  as  desired,  and  in  this  way  the  vehicle  is  steered.  The 
forward  position  of  these  levers  causes  power  to  be  transmitted 
through  the  steering  clutches;  the  rear  position  causes  it  to  go 
through  a  planetary  reducing  set;  while  the  control  position  dis- 
connects both  and  is  a  neutral  position.  With  one  lever  in  the 


394 


forward  position  and  the  other  in  the  rear  the  vehicle  will  turn 
in  the  direction  of  the  lever  in  the  rear  position.  With  one  lever 
in  either  the  forward  or  rear  position  and  the  other  in  the  central  or 
neutral  position  the  vehicle  can  be  turned  sharply  in  the  direction 
of  the  lever  in  the  neutral  position  by  applying  the  brake  foot 
pedal  on  that  side. 


The  speed  of  the  mount  is  controlled  primarily  by  the  gear-shift 
lever,  which  provides  for  two  speeds  forward  and  one  reverse. 
An  additional  or  secondary  reduction  can  be  obtained  for  each 
change-gear  lever  position  by  shifting  both  steering  levers  from 
their  forward  or  direct  position,  to  their  rear  position,  thereby 
engaging  the  planetary  reduction  to  both  tracks  simultaneously. 


395 


In  this  way  the  speed  can  be  reduced  for  a  momentary  pull  without 
disengaging  the  master  clutch  and  shifting  the  change-speed  gears. 
A  155-millimeter  gun  (Filloux),  model  of  1918,  with  its  regular 
top  carriage,  is  mounted  on  a  special  bottom  carriage  fastened  to  the 
main  frame  near  its  rear  end.  The  gun  has  about  5°  traverse,  both 


right  and  left,  between  the  top  and  bottom  carriages,  but  360° 
traverse  can  be  obtained  by  traversing  the  entire  vehicle  on  the 
ground.  A  traveling  lock  for  the  muzzle  end  of  the  gun  is  provided 
at  the  front  end  of  the  mount. 

A  more  detailed  description  of  the  gun  and  mount  will  be  found  on 
page  249. 


396 

Weights,  dimensions,  and  specifications. 

Weight  complete,  with  full  equipment __pounds__  62,000 

Weight  of  gun,  including  breech  mechanism do 8,  750 

Total  length  of  gun  (over  breech  face) inches—  232.9 

Maximum  range  of  gun yards__  17,  700 

Maximum  over-all  length,  with  gun inches—  254 

Maximum  over-all  height do 100 

Maximum  over-all  width : do 118.  5 

Center  of  gun  bore  above  ground do__  87 

Road  clearance do__  16 

Track : 

Weight  of  each  track,  right  or  left  (46  links) pounds__  '2,  576 

Center  to  center  of  tracks inches.  _  97 

Width  of  each  track  link do_—  18 

Ground  pressure,  hard  ground pounds  per  square  inch__  12.  7 

Ground  pressure,  3-inch  depression do 9.  7 

Minimum  turning  radius do 160 

Type  of  motor : 

Sterling  T-head  gasoline 145  horsepower  at  1,200  r.  p.  m. 

Number  of  cylinders 6 

Bore inches 5.  5 

Stroke __do__  6.75 

Horsepower  per  gross  ton 4.  75 

Road  speed  at  engine  speed  of  1,200  r.  p.  m.  to  1,500  r.  p.  m. 

Planetary  low  speed miles  per  hour 1.  3  1.  6 

Direct  low  speed __do 2. 9  3.  6 

Planetary  high  speed do 2.3  2.9 

Direct  high  speed do 5.  4  6.  75 

Planetary  reverse  speed do 1.5  1.8 

Direct  reverse  speed do 3.  4  4.  25 

Capacity  of  fuel  tank gallons 45 

Capacity  of  oil  tank do 5.  5 

Capacity  of  cooling  system do 20 

Gasoline  feed,  vacuum  tank. 

Ignition,  starting  by  battery  and  coil. 

Ignition,  operating,  Bosch  magneto. 

Carburetor,  Schebler  Model  A. 

Radiator,  Modine,  cellular  with  removable  sections. 


155-MILLIMETER  MOTOR  GUN  CARRIAGE  (CHRISTIE), 
MODEL  OF  1920. 


Upon  this  motor  carriage  is  mounted  the  155-millimeter  gun  (Fil- 
loux),  model  of  1918,  forming  a  combined  self-propelled  wheeled 
and  track  laying  vehicle,  in  which  the  power  is  transmitted  directly 
to  the  ground  through  the  drive  wheels  as  in  a  motor  truck,  or 
through  flexible,  endless  tracks  which  go  over  and  around  the  wheels. 

The  various  units  comprising  the  vehicle  are  assembled  on  the 
main  frame,  which  is  built  up  of  two  vertical  side  plates,  tied  to- 
gether by  three  vertical  transverse  plates,  two  horizontal  plates,  and 
a  hollow  axle. 

The  three  vertical  transverse  plates  are  located  in  the  driving  or 
rear  end  of  the  frame  and  form  two  boxes ;  one  of  which  houses  the 
engine  and  transmission,  and  the  other  the  radiator  unit. 


SIDE  ELEVATION   OF  MOUNT  IN   TRAVELING   POSITION. 

The  horizontal  plates  are  attached  to  the  side  plates,  one  above 
the  other,  near  their  lower  edge  and  to  the  front  of  the  vertical  trans- 
verse plates.  The  top  horizontal  plate  supports  the  base  plate,  upon 
which  the  gun  is  mounted. 

The  axle,  which  supports  the  steering  wheel  brackets  for  carrying 
the  front  steering  wheels,  is  located  near  the  bottom  and  at  the  front 
edge  of  the  vertical  side  plates. 

Power  is  furnished  by  a  6-cy Under,  4-cycle,  T-head  Christie  gaso- 
line engine,  which  develops  125  horsepower  at  1,200  revolutions  per 
minute.  The  engine  is  located  transversely  a  little  behind  the  center 
of  the  vehicle.  Ignition  is  by  dry  cell  batteries  and  coil,  when  start- 
ing the  engine, '  and  by  a  high-tension  Bosch  dual  magneto  when 

(397) 


398 

operating.  The  gasoline  system  consists  of  a  30-gallon  supply  tank 
and  Stewart  vacuum  tank  which  supplies  gas  to  a  Zenith  carburetor 
on  the  engine.  Cooling  is  accomplished  by  two  fans  and  a  radiator 
located  just  ahead  of  the  engine  in  the  frame.  The  engine  is  lubri- 
cated by  splash  from  the  crank  case. 

Each  drive  sprocket  obtains  its  power  from  the  engine  through  a 
separate  transmission  and  clutch.  The  clutches  are  of  the  dry  steel 
disk  type,  and  are  located  one  on  each  end  of  the  engine  crank  shaft. 
Each  transmission  consists  of  a  forward  and  reverse  gear  set,  a 
four-speed  change  gear  set,  and  an  internal  final  drive  gear  reduction, 
with  the  final  internal  gear  located  in  the  driving  wheel.  The  final 
drive  pinion  shafts  are  each  provided  with  an  external  band  brake 
for  stopping  or  steering  the  vehicle. 

The  vehicle  normally  is  driven  with  the  gun  breech  first,  but  can 
be  operated  in  either  direction.  The  vehicle  is  provided  with  four 
solid  rubber,  double-tired  wheels  on  each  side,  namely,  rear  driving 
wheel,  front  steering  wheel,  and  two  center  wheels.  The  two  center 
wheels  are  mounted  on  an  equalizer  bar  and  can  be  raised  clear  of 
the  ground  when  the  mount  is  operated  as  a  wheeled  vehicle,  or  can 
be  depressed  to  take  part  of  the  load  when  operating  as  a  track-laying 
vehicle.  When  operating  as  a  wheeled  vehicle  the  front  wheels  are 
steered  by  the  operator  in  the  same  manner  as  in  a  motor  truck. 
When  operating  as  a  track-laying  vehicle  the  steering  wheel  arms 
are  locked  in  a  central  position,  the  wheels  acting  as  idler  sprockets 
for  the  tracks. 

The  track  links  consist  of  an  endless  series  of  flat  shoes  equipped 
with  lugs  which  engage  the  driving  slots  of  the  driving  wheel  con- 
nected together  by  hardened  steel  pins.  The  driving  lugs  also  act 
as  guides  engaging  with  grooves  in  the  center  and  front  wheels. 
In  this  manner  the  track  is  kept  in  line  with  the  wheels.  When 
operating  as  a  wheeled  vehicle,  the  tracks  are  divided  and  removed 
and  carried  on  top  of  and  underneath  the  shelves  above  the  wheels.. 

The  change  gears  and  reverse  gears  are  shifted  by  hand  levers 
directly  in  front  of  the  driver  seat,  each  lever  controlling  similar 
sets  of  gears  in  the  right  and  left  transmissions.  When  operating 
as  a  track-laying  vehicle,  steering  is  accomplished  by  means  of 
steering  levers,  one  on  each  side  of  the  operator,  which  disconnect 
the  clutches  and  set  the  brakes,  and  can  be  operated  either  separately 
or  together.  By  shifting  only  one  steering  lever,  the  machine  turns 
in  the  direction  of  the  shifted  lever.  By  shifting  both  levers  together 
both  sides  are  either  in  a  neutral  position  with  the  brakes  set  or  both 
tracks  driving  together.  When  operating  as  a  wheeled  vehicle  the 
steering  handwheel  is  unlocked  and  operated  the  same  as  in  a  motor 
truck.  The  engine  controls  consist  of  spark  and  throttle  levers 
located  on  a  sector  beside  the  driver's  seat. 


399 


A  155-millimeter  (Filloux)  gun,  model  of  1918  (see  p.  249),  with 
its  standard  top  carriage,  is  mounted  on  a  special  bottom  carriage, 
fastened  to  the  main  frame  near  the  hollow  axle  at  the  front  of  the 


vehicle.     On  this  vehicle  the  gun  has  6°  left  and  7°  right  traverse 
between  the  top  and  bottom  carriages,  but  360°  traverse  can  be  ob- 
tained by  traversing  the  entire  vehicle  on  the  ground.     A  traveling 
lock  is  provided  for  the  gun  at  its  muzzle  end. 
55160—21 26 


400 

Weiffhis,  dimensions,  and  specifications. 

Weight  complete  with  full  equipment __pounds__  40,000 

Weight  of  gun.  including  breech  mechanism do 8,750 

Weight  on  front  wheels do 20,000 

Weight  on  rear  wheels do 20,000 

Total  length  of  gun  (over  breech  face) inches 232.9 

Maximum  range yards 17,  700 

Maximum  elevation degrees 35 

Maximum  traverse  __  do —    \ 

[  6  left 

Maximum  over-all  length  with  gun inches —  236 

Maximum  over-all  length  without  gun,  with  track do 204 

Maximum  over-all  length  without  gun,  without  track do 200 

Maximum  over-all  height do 80.  5 

Maximum  over-all  width do 116.75 

Center  line  of  trunnions  above  ground do 66.945 

Road  clearance do 12.  75 

Type  of  drive,  combination  wheeled  and  track  laying. 
Track : 

Weight  of  each  track __ pounds__  2,050 

Center  to  center  of  tracks inches—  89.25 

Width  of  track  shoes  (46  to  each  track) do 

Length  of  track  shoes  (46  to  each  track) do 9.75 

Ground  pressure,  hard  surface   (both  tracks) 

pounds  per  square  inch__  7.  216 

Ground  pressure  (tracks  on) do 5.63 

Wheels : 

[Inside     36x4.812(4if) 
Drive  wheels,  double-tired__  ..inches.-j^^  36  x  ?  812(7M) 

Center    wheels,    double-tired inches 36  x  4.  375 

Steering  wheels,  double-tired do 36  x  5.  812(511) 

Type  of  engine : 

Christie,  T-head,  gasoline horsepower 120 

Number  of  cylinders 6 

Bore inches.-          5$ 

Stroke do__  7 

Horsepower,  per  gross  ton 6 

Road  speeds  at  motor  speed  of  1,500  revolutions  per  minute : 
Forward   (breech  end  first)  — 

First  speed miles  per  hour 1.65 

Second  speed do 3.  5 

Third  speed ___do__          6.82 

Fourth  speed do__          11.5 

Reverse  (muzzle  end  first)  — 

First  speed miles  per  hour__      1.  39 

Second  speed do 2.89 

Third  speed __do__          5.69 

Fourth  speed __ do 9.61 

Capacity  of  fuel  tank gallons—          30 

Capacity  of  oil  tank do_—  10 

Capacity  of  cooling  system do 25 

.  Gasoline  feed,  vacuum. 
Ignition,  Bosch  magneto. 
Carburetor,  zenith. 
Radiator,  cellular. 


TRENCH  WARFARE  MATERIEL. 


The  trenches  constitute  the  most  advanced  position  of  a  combat 
army  and  the  equipment  and  supplies  placed  at  the  disposal  of  those 
occupying  them  are  generally  classified  under  the  broad  heading  of 
k'  Trench  warfare  materiel." 

The  trench  forms  protection  against  horizontal  firing  and  permits 
of  secret  massing  of  troops  for  surprise  attacks,  and  it  is  the  constant 
aim  of  the  Air  Service,  with  its  photographic  equipment  and  tele- 
graphic communications,  to  reduce  this  element  of  surprise.  Con- 
cealment of  the  general  outline  from  airplane  observation  is  impos- 
sible, but  details  may  be  concealed,  for  an  observer  in  an  airplane 
can  not  see  whether  a  trench  is  occupied  unless:  the  airplane  flies 
dangerously  low. 

The  trenches  are  carried  up  to  within  200  yards  or  less  of  the 
enemy's  front  line  and  are  the  scene  of  constant  watchfulness  to  pre- 
vent enemy  advance  and  of  constant  attempts  to  reduce  the  enemy 
personnel,  lower  his  morale,  capture  prisoners  for  the  purpose  of 
obtaining  information,  and  to  advance  the  position  of  our  own  lines. 

The  field  artillery  is  located  from  1  to  5  miles  or  more  behind  the 
front  line,  in  order  to  protect  it  from  sudden  rushes  by  the  enemy, 
while  the  infantry,  machine  gun,  and  trench  mortar  personnel  occupy 
the  trenches  interlaced  through  the  intervening  terrain  to  afford  this 
protection  and  also  to  place  the  personnel  of  the  army  in  a  position 
to  come  into  contact  with  the  enemy  without  being  obliged  to  pass 
over  a  wide  intervening  stretch  of  terrain  under  enemy  fire. 

The  operation  of  all  branches  of  the  service  are  interrelated,  and 
nothing  is  haphazard  or  independent  of  the  comprehensive  plan, 
save  during  the  heat  of  action  or  in  the  event  of  units  becoming 
isolated,  and  such  movements  are  only  temporary  in  their  inde- 
pendence, as  their  effects  are  consolidated  with  the  complete  plan 
as  soon  as  opportunity  permits.  The  air  service,  field  artillery,  the 
signal  service  and  the  tanks  are  all  coordinated  through  headquarters 
with  the  service  of  the  trenches,  and  communication  is  maintained 
through  an  elaborate  system  of  telephone  and  telegraph  wires,  pyro- 
technic flashlights,  flare,  or  other  visual  signals. 

The  trench  system  includes  a  front-line  trench  of  broken-line  for- 
mation, each  stretch  of  unbroken  line  being  from  9  feet  to  18  feet  in 
length.  An  enemy  entering  this  trench  can  sweep  only  the  length  of 

(40T) 


402 


TRENCH    WARFARE. 


403 

the  straight  line,  and  must  fight  around  a  barrier  for  the  balance  of 
the  trench.  This  trench  is  connected  by  communication  trenches 
to  a  supervision  trench  located  to  the  rear,  and  thence  by  other 
trenches,  possibly  several  miles  further  back,  into  friendly  territory. 
The  communication  trenches  are  curved,  elbowed,  or  zigzagged  and 
have  T  or  L  connections,  island  pockets,  tunnels,  bombing  pits, 
strong  points,  keeps,  shelters,  dugouts,  or  other  provisions,  as  the 
conditions  may  demand. 

Traps  are  arranged  for  the  confusion  of  an  enemy  entering  the 
trench,  positions  are  arranged  for  dropping  barbed  wire,  knives,  or 
frames  quickly  into  position  to  retard  the  advance  of  the  enemy 
troops  who  have  gained  the  trench.  Machine  gun  and  mortar  em- 
placements are  built  where  needed  and  bomb-proof  dugouts  provided 
for  rest  quarters,  storage  and  forward  dressing  stations  for  the 
treatment  of  wounded. 

The  narrower  a  trench  is  the  better  the  cover  which  it  affords. 
Communicating  trenches  are  made  of  sufficient  width  to  permit  of 


ARRANGEMENT   OF   TRENCHES. 

the  carrying  of  stretchers,  and  thus  allow  for  the  evacuating  of  the 
wounded  during  daylight.  The  wider  trench  submits  it  to  greater 
effect  from  enemy  artillery  fire,  but  if  trenches  are  not  wide  enough 
for  stretchers,  losses  result  through  the  detention  of  casualties  in 
the  trenches  until  darkness  permits  of  their  removal  to  dressing 
stations.  The  wider  trench  also  permits  a  more  rapid  movement  of 
men  and  supplies  between  the  front  line  and  rear  areas,  and  thus 
reduces  the  time  during  which  men  and  supplies  are  detained  under 
concentrated  fire,  and  hence  reduces  the  casualties  and  destruction 
from  this  cause. 

Gas  is  a  constant  menace  in  the  trenches,  as  it  is  heavier  than  air, 
and  its  effects  vary  with  the  nature  of  the  gas  employed.  Flame  or 
liquid  fire  is  employed  both  with  a  view  to  inflicting  injury  to  the 
enemy  and  lowering  his  morale.  The  presence  of  water  is  always 
taken  into  consideration,  for  the  trench  is  open  to  water  resulting  from 
rainfall.  Provisions  are  made  for  footing  and  drainage,  advantage 
being  taken  of  natural  slope  where  possible. 


404 

Trench  warfare  has  shown  the  necessity  for  hurling  large  charges 
of  high  explosives  for  comparatively  short  ranges.  This  m'cp.-.-itv 
has  led  to  the  development  of  the  trench  mortar,  a  type  of  weapon 
of  simple  construction  having  a  short  smooth  bore.  They  are  muz- 
zle loaders  and  use  as  their  projectile  a  thin-walled  shell,  knmvi 
a  trench -mortar  bomb. 

In  trench  warfare  the  role  of  trench  artillery  is  to  harass  the 
enemy  by  engaging  living  targets  where  opportunity  offers,  to  attack 
and  destroy  enemy  defensive  works  and  obstacles  within  range 
limits,  and  to  prevent  the  construction  of  new  works. 

The  trench  mortar  is  essentially  a  trench  artillery  weapon  of 
limited  range  which  will  render  very  efficient  service  when  properly 
emplaced  and  skillfully  handled  and  served. 

The  trench  mortars  are  divided  into  three  classes :  light,  medium, 
and  heavy  calibers. 

The  light  trench  mortar  is  very  mobile.  Its  effect  against  mate- 
rial is  inconsiderable,  but  is  particularly  effective  against  massed 
troops,  or  troops  driven  into  the  open,  due  to  its  rapidity  of  fire. 
These  mortars  are  used  to  form  a  barrage  behind  the  hostile  line  to 
prevent  reserves  and  ammunition  being  brought  up.  Owing  to  their 
high  mobility,  limited  only  by  the  difficulty  of  ammunition  supply, 
they  are  especially  fitted  to  accompany  the  infantry  as  it  advances, 
and  are  used  to  attack  machine-gun  shelters  and  other  points  which 
have  temporarily  checked  the  forward  movement  of  the  infantry. 

The  medium  trench  mortar,  with  its  range  of  approximately  1,700 
meters,  is  very  effective  against  wire  entanglements,  machine-gun 
shelters,  strong  points,  trenches,  and  other  similar  objectives  not 
too  strongly  protected. 

The  heavy  trench  mortar  is  designed  for  the  attack  of  heavily  pro- 
tected shelters  and  dugouts,  trenches,  machine-gun  shelters,  and 
strong  points.  It  is  seldom  used  against  wire  entanglements  because 
of  the  large  crater  formed  by  the  explosion. 

On  both  types  of  mortars  now  issued  to  the  service,  the  principle 
of  autoignition  is  employed.  This  principle  was  successfully  used 
on  the  British  Stokes  mortar  and  since  has  been  adopted  by  both 
the  French  and  our  armies.  Briefly,  the  method  of  applying  this 
principle  is  to  provide  a  firing  pin  in  the  breech  end  of  the  barrel 
against  which  the  shell,  carrying  the  propelling  charge  with  it. 
strikes  when  it  is  dropped  down  the  bore,  thus  automatically  firing 
the  propellent. 

The  types  now  issued  to  the  service  are : 
3-inch  Stokes  trench  mortar.  Mark  I. 
6-inch  trench  mortar,  Mark  I. 

The  characteristics  of  each  type  will  be  discussed  on  the  following 
pages. 


3-INCH  STOKES  TRENCH  MORTAR  (MARK  I). 


The  3-inch  Stokes  trench  mortar  is  of  British  origin,  and  proved  a 
very  useful  weapon  owing  to  its  simplicity,  light  weight,  and  the 
principle  of  autoignition. 


The  mortar  essentially  consists  of  the  following  components:  A 
smoothbore  barrel,  a  bipod,  and  a  base,  the  complete  unit  weighing 
110  pounds.  The  barrel  is  a  seamless-drawn  steel  tube,  lapped  to 

(405) 


406 

size  and  necked  down  at  one  end  called  the  breech  or  base  end. 
To  the  breech  end  is  fitted  a  base  cap,  within  which  is  secured  a 
firing  pin  protruding  into  the  barrel.  The  barrel  is  supported  near 
the  muzzle  end  by  a  steel  bipod  fitted  with  elevating  and  traversing 
screws.  The  recoil  of  the  mortar  is  taken  up  by  a  base  plate  against 
which  the  base  cap  of  the  barrel  rests. 


FRONT  VIEW  OF  TRENCH  MORTAR. 

The  bipod  is  made  of  tubular  steel,  consisting  of  two  legs  attached 
to  a  center  trunnion  by  means  of  a  compass  joint;  these  legs  are 
held  apart  by  a  cross  stay  which  is  arranged  to  spring  just  past 
the  dead  center  in  such  a  manner  as  to  hold  the  two  legs  rigidly 
apart.  The  trunnion  standard  is  fitted  with  a  pair  of  bevel  gears 
operated  by  a  handle,  by  means  of  which  the  elevating  screw  can 
be  rapidly  raised  or  lowered.  The  upper  end  of  the  elevating  screw 
is  fitted  with  a  yoke  to  support  the  traversing-screw  shaft,  which, 


407 

shaft  together  with  a  traversing  handle  and  a  dog  clutch,  forms  a 
bolt  held  in  position  by  a  locking  pin.  A  traversing  screw  car- 
ried by  the  traversing-screw  shaft  and  driven  by  the  dog  clutch 
forms  the  means  of  traversing  the  mortar  by  engaging  a  nut  fixed 
to  the  barrel.  The  barrel  can  be  quickly  disconnected  from  the 
mounting  by  lifting  the  locking  pin  and  withdrawing  the  travers- 
ing bolt.  The  barrel  may  then  be  lifted  out  of  position. 

The  base  plate  has  three  depressions.  The  shape  of  the  base  cap 
permits  the  lower  end  of  the  barrel  to  rest  in  any  of  these  depres- 
sions, and  by  shifting  the  barrel  from  one  to  another  a  change  of  6° 


REAR  VIEW  OF  TRENCH  MORTAR. 

in  direction  of  line  of  fire  can  be  made  on  either  side  of  the  center 
position. 

In  firing  position,  the  base  plate  is  embedded  in  the  ground  at 
about  a  45°  angle.  The  lower  end  of  the  barrel  is  placed  in  the 
indentation  in  the  base  plate  which  gives  the  direction  nearest  to 
that  desired,  the  upper  end  of  the  barrel  being  supported  by  the 
legs  of  the  bipod.  Minor  adjustment  for  direction  is  secured  by 
means  of  the  traversing  screw.  The  barrel  is  then  given  the  eleva- 
tion corresponding  to  the  desired  range  by  operating  the  elevating 
screw.  The  range  quadrant  (or  clinometer),  being  set  for  the  desired 
range,  indicates  when  the  barrel  has  the  proper  elevation. 


408 

The  shell  or  bomb  used  with  this  mortar  is  a  steel  cylinder  loaded 
with  high  explosive,  fitted  at  its  head  with  a  detonating  tu/i-.  The 
weight  of  the  shell  is  approximately  11£  pounds.  The  primary  pro- 
pelling charge  consists  of  a  12-gauge  shotgun  shell,  which  fits  in  a 
cartridge  container  at  the  rear  end  of  the  shell.  To  secure  addi- 
tional range,  1  to  3  rings  of  ballistite  can  be  placed  around  the  car- 
tridge container.  The  range  secured  with  the  cartridge  alone  varies 
from  150  yards  at  75°  to  300  yards  at  40°.  With  cartridge  and  three 
rings,  the  range  reaches  a  maximum  of  750  yards  at  40°  elevation. 

The  firing  operation  is  as  follows :  The  shell  with  propelling  charge 
in  position  (the  cartridge  inserted  in  the  cartridge  container  and  the 
rings  around  the  container)  is  dropped  into  the  muzzle  of  the  mortar, 
cartridge  end  first,  and  slides  down  the  barrel.  The  primer  of  the 
cartridge  is  fired  on  impact  with  the  firing  pin.  Ignition  of  the 
ballistite  rings  is  obtained  from  the  flash  of  the  cartridge  through 
ports  in  the  cartridge  container.  The  shell,  carrying  the  cartridge 
case  with  it,  is  projected  from  the  barrel  and  the  mortar  is  ready  for 
another  shell. 

The  extreme  rate  of  firing  under  average  conditions  is  about  25 
rounds  per  minute,  but  10  rounds  per  minute  is  considered  the 
average  effective  rate.  The  crater  formed  by  the  shell  has  a  depth 
of  about  2  feet  and  a  diameter  of  about  4  feet. 

Weights  of  mortar. 

Barrel,  ring,  clamp,  traversing  screw,  and  base  cap pounds—     43 

Bipod   (mounting  complete) do 37 

Base  plate_.  do__        30 


6-INCH  TRENCH  MORTAR  (MARK  I). 


This  mortar  is  an  American  adaptation  of  the  British  6-inch  New- 
ton trench  mortar.  The  principle  of  autoignition  is  again  employed 
on  this  type.  While  the  principle  of  firing  is  the  same  as  in  the 
3-inch  Stokes  mortar,  the  mounting  is  somewhat  different,  in  that  no 
bipod  is  employed.  This  weapon  is  a  most  effective  agent  against 
machine-gun  nests,  barbed-wire  entanglements,  fortifications,  etc.,  but 
is  seldom  used  against  personnel. 

This  mortar  consists  of  the  following  essential  components : 

Barrel  with  clinometer. 

The  platform,  base,  guys,  and  fittings. 

The  sub-base. 

The  barrel  is  of  one  piece,  muzzle  loading,  having  a  smooth  bore. 
The  breech  is  closed  and  rests  in  a  hemispherical  socket-shaped  steel 
base,  supported  upon  a  stationary  platform,  to  which  the  barrel  is 
stayed  by  three  adjustable  guys.  The  elevation,  which  varies  from 
a  maximum  of  75°  to  a  minimum  of  40°,  and  lateral  deviation,  are 
made  by  altering  the  length  of  the  guys,  which  are  adjustable  by  means 
of  handwheels.  These  adjustments  are  determined  by  the  setting  of 
the  clinometer  attached  to  the  barrel.  The  range  can  be  varied  by 
changing  either  the  elevation  of  the  gun  or  the  weight  of  the  pro- 
pelling charg«. 

The  setting  up  of  this  mortar  is  a  more  elaborate  proceeding  than 
that  of  the  3-inch  Stokes  mortar.  Various  methods  of  installation 
for  this  mortar  are  shown  on  page  410.  It  will  be  noticed  that  in  some 
cases  the  sub-base  may  be  dispensed  with.  This  depends  entirely 
upon  the  nature  of  the  terrain  and  the  conditions  under  which  the 
mortar  is  fired. 

The  barrel  is  furnished  internally  at  the  breech  end  with  an  axial 
firing  pin  and  externally  with  a  guide  stud  and  a  misfire  plug. 
Should  the  ignition  cartridge  fail  to  function  when  the  shell  is 
dropped  down  the  barrel,  the  misfire  plug  permits  of  the  introduction 
of  a  small  powder  charge  with  fuze  for  the  ignition  of  the  propelling 
charge.  Graduations  are  engraved  on  the  barrel  on  the  right  and 
left  of  a  zero  line  and  are  used  for  traverse  setting  of  the  clinometer. 

(409) 


410 


411 

The  base  is  a  steel  casting  having  a  machined  hemispherical  socket 
on  the  upper  side  to  receive  the  rounded  end  of  the  barrel  and  pro- 
vided with  a  guide  groove  which  engages  the  guide  stud  on  the  barrel 
when  in  position. 

The  base  is  bolted  to  the  hardwood  platform.  Elevating  and 
traversing  guys  are  anchored  to  the  upper  side  of  the  platform,  while 
the  free  ends  of  the  guys  are  hooked  into  devices  on  the  barrel  when 
the  latter  is  mounted  on  the  base.  Special  hooks  provide  a  method 


LEFT   SIDE  VIEW   OF   6-INCH   TRENCH  MORTAR. 

of  fastening  the  guys  during  transportation.  Four  wire-rope  han- 
dles are  provided  as  a  means  for  carrying  the  platform. 

The  clinometer  consists  of  a  quadrant  graduated  with  an  elevation 
scale  and  straddled  by  a  level-vial  carrier  which  oscillates  about  a 
center  on  the  quadrant.  The  level- vial  carrier  is  provided  with  a  pair 
of  cross  level  vials.  The  clinometer  is  attached  to  the  mortar  barrel 
by  steel  bands  and  a  clamping  screw. 

To  lay  the  piece  an  indicating  line  on  the  quadrant  is  set  to  the 
desired  traverse  on  the  traverse  scale  on  the  barrel,  and  the  indicator 
on  the  level- vial  carrier  is  set  coincident  with  the  desired  elevation  on 


412 

the  elevation  scale  on  the  quadrant.  The  guys  are  then  adjusted 
so  that  both  vials  show  an  exact  level.  The  barrel  of  the  mortar  then 
points  in  the  desired  direction. 

The  gas  ejector  consists  of  a  metal  head,  to  fit  the  bore,  fastened 
to  one  end  of  a  long  tube  at  the  other  end  of  which  is  a  handle. 
When  the  gas  ejector  is  pushed  down  the  barrel  the  burned  <r;iM-> 
are  forced  up  through  the  handle  and  out  of  the  gun.  When  the 
gas  ejector  is  drawn  out,  cold  air  is  sucked  through  the  handle  and 


METHOD  OF  LOADING  TRENCH  MORTAR. 

into  the  gun.  The  head  is  threaded  to  receive  a  wire  brush  or  a 
sponge  head  whenever  it  is  desirable  to  clean  or  sponge  out  the  bore. 

The  projectile  is  a  cast-iron  fragmentation  shell  with  vanes,  weigh- 
ing approximately  53  pounds  loaded,  and  containing  a  bursting 
charge  of  approximately  11  pounds  of  high  explosive.  The  projec- 
tiles are  fitted  with  delay  and  nondelay  fuzes. 

The  propelling  charge  consists  of  sporting  ballistite  contained  in 
silk  bags  of  1  and  2  ounces  capacity.  With  these  two  sizes  of  bags 
a  number  of  combinations  can  be  obtained  and  the  range  varied 
accordingly.  The  maximum  charge  is  9  ounces  and  the  minimum  3 


413 


ounces.  The  bags  are  held  in  place  between  the  vanes  of  the  shell 
by  a  propelling  charge  bag  holder.  The  charge  is  ignited  by  an 
ignition  cartridge  made  from  a  standard  rifle  cartridge  which  is 
fired  by  impact  with  the  firing  pin  when  the  shell  reaches  the  bottom 
of  the  barrel. 


REAR  VIEW   OF  MORTAR. 

Weights,  ballistics,  <-1<: 

Over-all  length  of  barrel inches 57 

Weight  of  barrel pounds 162 

Weight  of  base do 75 

Weight  of  platform do 160 

Weight  of  sub-base , do 530 

\Veightofshell,  loaded   (approximately) do 53 

Weight  of  shell  box do 10 

Range,  minimum meters 200 

Range,  maximum do 1,  700 


PROSPECTUS. 


All  wars  have  stimulated  the  development  of  implements  of  war- 
fare. During  the  recent  World  War  new  implements  of  war  have 
been  conceived  and  developed,  while  others  have  been  given  the 
supreme  test  and  found  capable  of  further  development.  Of  the 
problems  arising  from  the  war  none  is  more  important  or  more  in- 
teresting than  the  development  of  artillery  materiel.  In  analyzing 
it,  a  brief  consideration  of  its  state  before  the  war  and  the  effect  of 
the  World  War  upon  it,  both  in  this  country  and  abroad,  is  necessary. 

The  field  gun  with  which  our  Army  was  equipped  prior  to  1917 
was  developed  about  1902  to  meet  the  demands  for  a  stable  gun  car- 
riage— one  in  which  the  aiming  of  the  piece  was  not  disturbed  by  the 
shock  of  firing.  From  then  on,  no  marked  developments  in  design 
took  place  until  the  invention  of  the  split-trail  carriage,  by  which 
large  increase  in  both  traverse  and  elevation  of  the  piece  was  made 
possible.  In  1912  the  design  of  such  a  carriage  was  initiated,  which, 
after  exhaustive  tests,  was  put  into  production  late  in  1916. 

The  design  of  howitzers  and  medium-caliber  guns  was  limited  by 
road  conditions  in  this  country.  In  these  pieces  power  was  sacrificed 
to  obtain  the  necessary  mobility.  It  had  generally  been  considered 
impracticable  to  use  heavy  siege  guns  and  howitzers  in  the  field  on 
this  continent;  therefore,  none  had  been  provided  for  our  mobile 
troops. 

Practically  all  French  and  British  designs  for  practically  all  cali- 
bers of  guns  and  howitzers  were  adopted  for  war  manufacture.  The 
French  75-millimeter  field  gun  was  put  into  production  because  the 
American  split-trail  carriage  had  not  been  thoroughly  tried  out  in 
service,  and  the  British  75  was  ordered  because  production  facilities 
were  available. 

The  United  States  entered  the  war  with  neither  an  adequate  engi- 
neering force  to  develop  new  designs  nor  a  trained  production  force 
to  organize  manufacture.  It  had  merely  a  handful  of  materiel  and 
practically  no  facilities  to  produce  more.  Our  allies  not  only  furnished 
us  materiel,  but  gave  us  their  designs  and  production  engineers  to 
assist  us  in  organizing  production.  Most  of  our  engineering  talent 
was  required  to  solve  the  problems  of  production.  Although  work- 
ing under  war  pressure,  time  was  too  short  to  secure  results.  Had 
the  war  continued,  some  real  development  work  might  have  been 
accomplished  with  the  large,  earnest  organization  built  up  during 
the  war. 

(414) 


415 

Considerable  development  of  new  types  of  materiel  was  carried  out 
both  here  and  abroad,  but  as  far  as  pertains  to  mobile  artillery  the 
war  mainly  was  fought  with  pre-war  types  of  field  pieces.  The  out- 
standing accomplishment  was  the  introduction  by  the  French  of  the 
"  G.  P.  F."  and  their  antiaircraft  artillery. 

The  British  gradually  improved  the  range  characteristics  of  their 
artillery  and  had  under  way  an  excellent  design  of  a  new  field  gun. 

The  Germans  easily  ranked  first  in  the  development  of  artillery 
during  the  war.  They  developed  and  manufactured  greatly  im- 
proved pieces  of  all  calibers.  They  recognized  the  value  of  range,  not 
only  in  the  design  of  more  powerful  guns  of  a  given  caliber,  but  also 
in  mounting  these  guns  on  carriages  so  that  their  maximum  range 
could  be  secured.  By  the  use  of  these  pieces  the  Germans  caused 
much  concern  to  the  allied  artillery  commanders. 

Prior  to  the  war,  progress  in  the  mechanical  arts  caused  by  the 
development  of  the  gas  engine  had  had  no  appreciable  effect  upon 
the  design  of  artillery  materiel.  The  field  piece  had  been  conceived 
in  terms  of  the  horse,  the  mountain  howitzer  in  terms  of  the  pack 
mule,  therefore  very  little  progress  had  been  deemed  possible  as  the 
horse  was  a  fixed  quantity.  The  perfection  of  the  gas  engine,  how- 
ever, removed  the  horse  as  a  limiting  factor.  The  development  of 
the  automobile  industry  permitted  high  speeds  of  vehicle  propul- 
sion, and  created  a  demand  for  alloy  steels  of  high  physical  prop- 
erties. All  these  factors  became  important  to  artillerymen,  for  it 
is  evident  that  mechanical  traction  permits  the  increased  weights 
required  for  long-range  artillery;  increased  speed  permits  rapid 
strategic  concentration  of  artillery;  high-grade  steels  permit  greater 
power  in  guns. 

Since  the  armistice  the  sentiment  of  our  artillerymen  is  unani- 
mously in  favor  of  pieces  of  greater  range,  greater  elevation,  and 
greater  mobility.  This  sentiment  found  expression  in  the  reports 
of  the  various  service  boards  and  especially  in  that  of  the  Wester- 
velt  board.  The  report  of  this  board  was  approved  by  the  Chief 
of  Staff,  and  its  recommendations  have  become  the  fundamental 
specifications  for  mobile  artillery  materiel.  Ever  since,  the  efforts 
of  the  ordnance  engineer  have  been  devoted  mostly  to  the  develop- 
ment of  design  under  the  Westervelt  board  program.  Under  that 
program  the  same  calibers  of  pieces  as  used  during  the  war  will  be 
developed,  but  they  will  have  greater  range,  greater  flexibility  of 
mount,  and  greater  mobility. 

Longer  range  will  be  attained  partly  through  ammunition  de- 
velopment, and  partly  by  increase  in  the  length  and  muzzle  velocity 
and  elevation  of  the  gun.  As  mobility  requires  lightness,  the  weight 
of  the  gun  will  be  reduced  as  much  as  possible.  To  secure  this,  three 

5516O— 21 27 


416 

lines  of  development  are  being  followed :  First,  by  using  material  of 
higher  physical  qualities;  second,  by  wire- wrapping  the  tube;  and 
third,  by  the  "  auto-frettage  "  process. 

At  present,  no  new  problems  are  involved  in  the  construction  of 
the  wire-wrapped  gun.  By  the  use  of  wire,  lower-grade  metal  can 
be  utilized  in  the  forgings.  Guns  made  by  this  process  are  slightly 
heavier  than  those  made  of  chrome  alloy  steel. 

In  the  auto-frettage  method  of  construction,  the  gun  is  built  up 
of  a  few  pieces  of  steel  of  medium  physical  qualities.  The  walls  of 
the  gun  are  internally  stressed  beyond  their  elastic  limit  by  internal 
hydraulic  pressure.  The  condition  set  up  is  similar  to  that  pro- 
duced by  the  shrinking  process.  The  process  is  also  a  cheaper  one 
than  either  the  built-up  or  the  wire- wrapped  method  of  construction. 

Much  research  work  still  remains  to  be  done  in  determining  the 
proper  form  of  rifling,  the  effect  of  variation  of  elements  of  the 
bore  upon  the  life  of  the  gun,  the  production  and  heat-treating 
of  metals  used  in  gun  construction,  and  in  checking  the  fundamental 
formulae  of  gun  design. 

The  trend  of  design  for  field  artillery  now  proposed  and  under 
way  shows  several  digressions  from  the  present  practice : 

Motor  transportation  promises  to  almost  completely  revolutionize 
artillery  design.  A  motor-drawn  carriage  is  not  so  limited  in  weight 
as  the  horse-drawn  type,  thus  permitting  heavier  and  more  powerful 
weapons.  At  the  same  time  the  carriage  must  be  designed  to  with- 
stand the  more  severe  usage  of  motor  traction. 

For  pack  howitzers,  and  field  and  siege  pieces  of  75-millimeter  and 
greater  caliber,  the  hydropneumatic  recuperator  is  being  employed. 
The  St.  Chamond-type  recuperator  is  used  for  75  and  105-millimeter 
calibers  and  the  Filloux-type  for  4.7-inch  to  8-inch  calibers.  New 
developments  have  not  been  made  in  these  types  since  the  armistice. 
They  have  been  merely  adapted  to  meet  the  new  conditions  imposed. 

During  the  war  great  difficulty  was  experienced  in  the  production 
of  recuperators.  Because  of  the  use  of  oil  and  air  under  high  initial 
pressure  extremely  fine  workmanship  was  required  in  the  finishing 
of  the  bore  of  cylinders  and  in  the  manufacturing  of  pistons.  De- 
velopment along  these  lines  is  being  carried  on  in  which  the  air  is  con- 
fined in  a  metal  bellows,  thereby  eliminating  the  complex  pistons  now 
necessary.  Such  a  system  also  offers  much  simpler  production  prob- 
lems in  the  degree  of  finish  required  in  the  bores  of  the  recuperators. 

Two  independent  lines  of  carriage  development  are  being  pursued — 
the  wheel  type  and  the  caterpillar  type.  Common,  desirable  charac- 
teristics are  high  elevation,  wide  traverse,  a  minimum  depth  of  pit 
for  clearance  of  recoil  parts  at  high  elevation,  and  stability  at  all 
elevations.  The  condition  of  high  elevation  and  minimum  depth  of 
pit  has  necessitated  placing  the  center  of  trunnions  of  the  tipping 


417 

parts  in  the  rear  of  their  center  of  gravity,  and  equalizing  the  forces 
required  to  elevate  and  depress  by  an  equilibrating  system.  Although 
the  equilibrating  system  adds  weight  and  complexity  to  the  gun  car- 
riage, the  advantages  thus  derived  more  than  offset  the  former. 
Bringing  the  center  of  rotation  of  the  gun  to  the  rear  and  the  use  of 
variable  recoil  permits  lowering  the  axis  of  the  gun,  which  is  ad- 
vantageous in  permitting  lightness  of  construction  and  shortening 
of  the  trail. 

Wide  traverse  has  resulted  from  the  use  of  the  split  trail  at  the  ex- 
pense of  weight  and  simplicity  of  construction.  The  split  trail  75- 
millimeter  carriage  weighs  about  700  pounds  more  than  the  box  trail 
carriage.  This  is  due  partly  to  the  greater  elevation — 80°,  compared 
with  45°.  Provisions  for  elevating  the  pieces  beyond  that  required  for 
maximum  range  is  causing  complication  of  design  and  increased 
weights.  The  bottom  carriage  must  be  built  out  farther  from  the 
axle  to  permit  clearance  at  the  higher  elevations,  and  this  is  expensive 
in  weight. 

The  Westervelt  board  report  contemplates  a  gun  and  a  howitzer 
mounted  on  the  same  carriage.  This  simplifies  production  and  sup- 
ply, but  complicates  the  design  of  the  carriage.  It  is  difficult  to 
secure  the  same  reactions  in  the  carriage  from  both  gun  and  howitzer. 
For  example,  the  4.7-inch  gun  materiel  is  heavier  than  it  need  be 
because  the  155-millimeter  howitzer  demands  a  heavier  carriage. 
The  ideal  of  the  artilleryman  is  the  reduction  of  the  number  of 
calibers  to  a  minimum  and  the  standardization  of  mounts.  The  de- 
sirability of  such  a  program  is  apparent  to  the  department  charged 
with  production  and  maintenance.  However,  the  mission  of  the  piece, 
not  the  desirability  of  standardization,  must  fix  its  characteristics. 

Marked  development  is  being  attempted  in  sighting  systems.  The 
field-gun  sight  follows  in  principle  that  developed  for  the  75-milli- 
meter model  of  1916  materiel,  but  is  much  more  compact,  and  the  sight 
for  heavier  guns  will  be  a  modified  quadrant  sight  like  that  used  on 
the  155-millimeter  howitzer  but  with  a  panoramic  sight.  For  accom- 
panying fire-control  instruments  various  improvements  are  now  in 
progress. 

In  the  war  models  of  motor-carriage  mounts  little  attention  could 
be  given  to  reduction  in  weight  and  to  refinement  in  design.  The 
possibilities  of  development  of  these  types  of  gun  mounts  should  not 
therefore  be  judged  by  the  materiel  built  under  war  contracts,  nor 
even  by  that  now  being  constructed.  Especially  such  essential  char- 
acteristics as  accessibility  of  parts  for  maintenance  and  elimination 
of  mechanical  weakness  in  details  of  construction  must  be  worked 
out  by  experience.  In  considering  any  model  the  possibilities  of 
perfecting  the  design  into  a  desirable  machine  must  be  given  the 
greatest  weight. 


418 

Motor-carriage  development  is  now  proceeding  along  two  lines: 
first,  the  track-laying  type  found  in  tractors;  and  second,  a  combina- 
tion wheel  and  track-laying  type  in  which  the  mount  may  be  operated 
on  wheels  on  good  roads  or  on  tracks  where  road  conditions  are 
bad.  Both  types  are  self-propelled  and  have  similar  gun  character- 
istics; weights  are  about  the  same;  speeds  are  similar  off  roads; 
while  the  second  type  promises  greater  speeds  over  good  roads. 
Because  of  the  promise  of  both  types,  light  and  heavy  gun-pilot  ma- 
teriels  of  both  are  being  built.  75-millimeter  gun  and  105-milli- 
meter howitzer  carriages  have  been  designed  and  built  by  the  Holt 
Caterpillar  Company  and  by  the  Front  Drive  Motor  Company. 
Good  comparative  tests  of  the  two  principles  of  construction  should 
be  obtained  from  these  pilots. 

The  ideal  traverse  as  expressed  by  the  Westervelt  board  report 
is  360°.  This  is  being  secured  only  in  antiaircraft  mounts  in  which 
the  gun  is  pivoted  on  a  pedestal.  Mounting  guns  on  a  pivot  like 
that  in  the  antiaircraft  mount  requires  increased  height  of  trun- 
nions and  heavy  mounts. 

In  the  infantry  accompanying  howitzer  an  attempt  is  being  made 
to  develop  a  piece  which  can  be  used  either  as  a  direct-fire  gun 
against  tanks  or  as  a  howitzer,  taking  the  place  of  the  3 -inch  trench 
mortar.  Guns  of  both  1.8-inch  and  2.24-inch  caliber  are  under  test. 
They  will  be  capable  of  being  broken  up  into  man  loads. 

Two  calibers  of  antiaircraft  guns  are  being  developed — 3-inch  and 
4.7-inch.  The  sighting  system  permits  the  application  of  azimuth 
and  elevation  corrections  and  superelevation  without  disturbing  the 
pointing  of  the  sight.  Compressed  air  will  be  used  for  loading.  In 
the  heavier  gun,  a  muzzle  brake  will  be  developed  in  order  to  lessen 
the  load  on  the  recuperator.  With  other  guns,  almost  85  per  cent  of 
the  recoil  energy  has  been  absorbed  in  a  muzzle  brake,  but  only  about 
half  that  efficiency  is  expected  in  this  case.  For  antiaircraft  work, 
another  big  problem  is  to  develop  a  satisfactory  sighting  and  fire- 
control  system. 

The  latest  development  in  sighting  systems  for  antiaircraft  artil- 
lery involves  the  removal  of  all  sighting  instruments  from  the  car- 
riage and  the  furnishing  of  graduated  scales  only  for  elevation  and 
traverse,  thus  eliminating  the  greatest  cause  of  complexity  in  the  gun 
mounts.  The  piece  will  be  laid  entirely  by  indirect  fire  methods  from 
data  furnished  from  a  central  station. 

In  general,  it  will  be  seen  from  the  above  that  future  artillery 
will  more  nearly  approach  the  ideal,  to  the  degree  that  the  prin- 
ciples of  high  power  and  swift  transportation  are  incorporated  in 
the  design.  In  war  the  former  is  probably  the  first  demanded, 
although  in  time  of  peace  it  is  sometimes  overshadowed  by  the  latter. 


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